Reinforced Pressure Vessel

Abstract

The pressure vessel (4) A liner (6) defining an interior fluid storage chamber (3), a generally cylindrical central portion (8) having a first outer diameter D1 at a first longitudinal end (8a); a first domed longitudinal end (12) having a base (12a) of a second outer diameter D2, the second outer diameter D2 being smaller than the first outer diameter D1; a first intermediate portion (13) located between the generally cylindrical central portion (8) and the first dome-shaped longitudinal end portion (12) and connecting the first longitudinal end portion (8a) of the generally cylindrical central portion (8) to a base (12a) of the first dome-shaped longitudinal end portion (12); a liner (6), a first domed longitudinal end (12) of the liner (6) having a dome profile that is less concave toward the interior fluid storage chamber (3) than a domed longitudinal end having a geodesic dome profile; a first dome reinforced shell (16) having a shape complementary to the shapes of both the first dome-shaped longitudinal end (12) and the first intermediate portion (13) of the liner (6), the first dome reinforced shell (16) being fitted to both the first dome-shaped longitudinal end (12) and the first intermediate portion (13) of the liner (6); Boss (14) and an outer composite structure (20) that encloses or encapsulates the liner (6) and the first dome reinforced shell (16); Equipped with.

Description

[Technical field]

[0001] The present invention relates to a pressure vessel for a vehicle. More precisely, the invention relates to a pressure vessel and a vehicle equipped with such a pressure vessel. [Background technology]

[0002] High pressure vessels for vehicles generally comprise a hollow housing, also called a liner, having a generally cylindrical shape with two domed longitudinal ends, and made of a plastic material, chosen for its light weight and low manufacturing costs, or other materials such as metal (e.g., aluminum). The housing is intended to store gas under pressure, e.g., dihydrogen, to be used by the vehicle equipped with the pressure vessel for various functions such as power supply. Gas under pressure exerts strong constraints against the interior surface of the housing, thereby compromising the integrity of the housing and may result in dangerous leaks, especially in the case of combustible gases such as dihydrogen.

[0003] To improve the mechanical properties of the housing, it is known to wind filaments made of reinforcing fibers, for example carbon fibers, over the entire outer surface of the housing, the filaments being embedded in a resin to facilitate winding and ensure that each piece of the outer surface of the housing is covered.

[0004] For the domed longitudinal ends of the housing, it is known to manufacture a domed reinforcement or a domed reinforced shell with a winding of filaments independently of the housing and to fit the domed reinforced shell onto the housing in a subsequent step. US Pat. No. 5,399,433 gives an example of such a domed reinforced shell. When using such a domed reinforced shell, the domed longitudinal ends of the housing and the domed reinforced shell are given a geodesic dome profile in order to generate a constant tension in the wound reinforcing fibers at all points of the length of the fibers. However, this profile has some disadvantages.

[0005] The presence of the dome reinforced shell locally increases stress concentrations within the wound reinforcing fibers, especially in the tip region of the dome reinforced shell, thereby necessitating the use of more reinforcing fibers than would be necessary without the dome reinforced shell, which is undesirable because it increases the cost, time to manufacture the pressure vessel, and increases the weight of the resulting vessel. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] DE10 2017 208 492 A1 [Non-patent literature]

[0007] [Non-Patent Document 1] Stuart M. Lee, "Handbook of Composite Reinforcements", ISBN: 0-471-18861-1, pp. 244-245 Summary of the Invention [Problem to be solved by the invention]

[0008] In view of the above, there is a need to optimize pressure vessels by reducing the amount of reinforcing fibers used while maintaining good mechanical properties. [Means for solving the problem]

[0009] For this purpose, according to the invention, there is provided a pressure vessel, comprising: A liner defining an interior fluid storage chamber, comprising: a generally cylindrical central portion having a first outer diameter D1 at a first longitudinal end; a first domed longitudinal end having a base with a second outer diameter D2, the second outer diameter D2 being smaller than the first outer diameter D1; a first intermediate portion located between the generally cylindrical central portion and the first dome-shaped longitudinal end, the first intermediate portion connecting the first longitudinal end of the generally cylindrical central portion to a base of the first dome-shaped longitudinal end; a liner, the first domed longitudinal end of the liner having a dome profile that is less concave toward an interior fluid storage chamber than a domed longitudinal end having a geodesic dome profile; a first dome reinforced shell having a shape complementary to the shape of both the first dome shaped longitudinal end and the first intermediate portion of the liner, the first dome reinforced shell mating with both the first dome shaped longitudinal end and the first intermediate portion of the liner; With the boss, an outer composite structure that encloses or encapsulates the liner and the first dome reinforced shell; A pressure vessel comprising:

[0010] Due to the complementary shape of the first dome reinforced shell, the mechanical properties of the pressure vessel are improved by reinforcing the first dome-shaped longitudinal end and the first intermediate portion. In particular, stresses are reduced within the outer composite structure and within the first dome reinforced shell. This allows the first dome reinforced shell to be manufactured and the outer composite structure to use fewer fibers while maintaining good mechanical properties. This reduces the weight of the resulting pressure vessel. Furthermore, this allows the manufacturing time to be reduced, since it takes less time to wrap the outer composite structure around the liner and the first dome reinforced shell.

[0011] In addition, due to the difference in diameter between the first outer diameter D1 and the second outer diameter D2, an insertion area is formed in the first intermediate portion, which prevents the first dome reinforced shell from being flush with the liner or from protruding too much, thereby avoiding excessive stresses inside the outer composite structure at the point where the first dome reinforced shell protrudes. In a preferred embodiment, the first outer diameter D1 and the second outer diameter D2 are such that the first dome reinforced shell is flush with the liner. The outer surface of the pressure vessel is therefore particularly smooth. This improves the attachment of the outer composite structure and reduces the stress level in the pressure vessel.

[0012] The phrase "the first dome reinforced shell is flush with the liner" means that the outer surface of the liner geometrically merges with the outer surface of the first dome reinforced shell.

[0013] The expression "filament" refers to continuous fiber tows, preferably carbon, glass, or aramid fibers, that are either impregnated with a liquid matrix to form a composite or are not pre-impregnated (i.e., dry fibers). Depending on the type of matrix used, there are two main families of composites: thermoset composites and thermoplastic composites, which are formed using a thermosetting resin or a thermoplastic polymer as the matrix.

[0014] Thermoset resins are formed by mixing two or more reactive components that form reactive thermoset precursors that react to exposure to curing conditions (e.g., heat, UV, or other radiation, or simply by contacting each other) to form a thermoset resin. The thermoset matrix must be fully cured to produce a high-performance composite. After curing, the thermoset resin becomes solid and cannot be further processed or reshaped because the resin can no longer flow. Examples of thermoset resins include unsaturated polyester, epoxy, vinyl ester, polyurea, isocyanurate, and polyurethane resins. It is possible to create a thermoset prepreg made of fibers impregnated with reactive resins that are only partially cured so that they are tacky but still soft. The prepreg can be stored and later further processed under pressure by heating or exposing the resin to UV to complete the curing and solidification of the prepreg.

[0015] Thermoplastic polymers can change from a solid (or non-flowing) state to a liquid (or flowing) state and from a liquid to a solid state by increasing or decreasing the temperature, respectively. For semi-crystalline polymers, decreasing the temperature of the thermoplastic will cause crystals to form and the thermoplastic to solidify. Conversely, heating a semi-crystalline polymer to a temperature above its melting point will cause the crystals to melt and the thermoplastic to flow. Examples of semi-crystalline thermoplastics include polyetherketones such as polyetheretherketone (PEEK), polyetherketoneketone (PEKK), polyetherketoneketoneetherketone (PEKKEK), polyamides such as polyamide 6 (PA6), polyamide 66 (PA66), polyamide 10 (PA10), polyamide 11 (PA11), polyamide 12 (PA12), polyolefins such as polyethylene (PE), polypropylene (PP), etc. Amorphous thermoplastics do not form crystals and do not have a melting point. Amorphous thermoplastics either solidify or flow depending on whether the material temperature is above or below its glass transition temperature. Examples of amorphous thermoplastics include polyetherimide (PEI), polysulfone (PSU), polyethersulfone (PES), polycarbonate (PC), polystyrene (PS), thermoplastic polyurethane (TPU), etc. Thus, both semi-crystalline and amorphous thermoplastics can be reshaped by heating above their melting or glass transition temperatures, and can be frozen into new shapes by lowering the temperature depending on their melting or glass transition temperatures. Although not strictly correct from a physical point of view, for ease of explanation, both semi-crystalline and amorphous thermoplastics in the liquid state are referred to herein as "thermoplastic melts."

[0016] The liner may be made of any material conventionally used in pressure vessels, particularly for vehicular pressure vessels, For example, the liner may be made of a metal, such as aluminum or steel, or may be made of a plastic.

[0017] The first dome reinforced shell is, for example, the dome reinforced shell described in the above-mentioned prior art document.

[0018] In the context of the present invention, a geodesic dome refers to a dome structure based on a network of great circles on the surface of a hemisphere. The geodesics intersect to form triangular elements that have local triangular stiffness and distribute stresses throughout the structure. Geodesic dome profiles can be produced by the techniques described in "A geodesic dome structure: a method for the construction of a geodesic dome" (p. 2002). Geodesic dome profiles allow for isotensile loading of the filaments.

[0019] The term "constant tension" refers to the characteristic of a fully wrapped pressure vessel in which each filament of the outer composite structure wrapped around the liner and first dome reinforced shell is subjected to a constant pressure at every point in its path. In this configuration, virtually all of the stress imposed on the vessel by the compressed interior fluid is borne by the filaments of the outer composite structure, with much less stress borne by the liner.

[0020] Because the first dome reinforced shell has a shape complementary to the shape of the first dome-shaped longitudinal end of the liner, the first dome reinforced shell also has a dome contour that is less concave toward the interior fluid storage chamber than a dome reinforced shell having a geodesic dome contour.

[0021] Advantageously, the shape of the first intermediate portion of the liner has an outer circumferential surface selected from the group consisting of a cylindrical shape, a frusto-conical shape, a curved shape, and combinations thereof.

[0022] Thus, the outer surface of the liner with the first dome reinforced shell is particularly smooth, which improves the attachment of the outer composite structure and reduces the stress levels within the pressure vessel.

[0023] Preferably, the outer circumferential surface of the first intermediate portion is a combination of a first frustoconical surface and a first cylindrical surface.

[0024] The liner may therefore be considered a stepped liner with a first tapered outer shoulder between a generally cylindrical central portion and a first dome-shaped longitudinal end.

[0025] Advantageously, the angle γ formed between the first frustoconical surface and the first cylindrical surface of the first intermediate portion is less than 15°, preferably less than 10°.

[0026] The angle facilitates a smooth transition from the first frustoconical surface to the first cylindrical surface of the first intermediate portion and avoids the formation of sharp edges that could damage the outer composite structure. The angle also facilitates reducing stresses in a tip region of the first dome reinforced shell within the liner.

[0027] Advantageously, the angle σ formed between the first frustoconical surface and the outer circumferential surface of the substantially cylindrical central portion is less than 15°, preferably less than 10°.

[0028] This angle provides a smooth transition from the first frustoconical surface to the outer periphery of the generally cylindrical central portion and avoids the formation of sharp edges that could damage the outer composite structure. Additionally, when the first intermediate portion includes a first tapered outer shoulder for receiving the tip of the first dome reinforced shell, this angle reduces stresses in the tip region of the first dome reinforced shell within the liner.

[0029] Preferably, the maximum distance between the dome contour of the first dome-shaped longitudinal end and the dome contour of the dome-shaped longitudinal end having a geodesic dome contour is comprised between 0.1% and 5% of the first outer diameter D1, preferably between 0.5% and 2.5% of the first outer diameter D1.

[0030] These values ​​are suitable for the first dome-shaped longitudinal end and are easily implemented in the manufacture of the liner, allowing for a better reduction in stresses in the outer composite structure that encloses or encapsulates the liner and the first dome-reinforced shell, which in turn allows for less composite structure to be used.

[0031] In another embodiment, the pressure vessel further comprises a hoop layer wrapped around the generally cylindrical central portion of the liner, whereby the first outer diameter D1 includes the hoop layer.

[0032] This configuration allows the liner to be a conventional liner rather than a stepped liner, which is a liner that does not have a step.

[0033] In a preferred embodiment, the pressure vessel comprises: Raina, a third outer diameter at a second longitudinal end opposite the first longitudinal end of the generally cylindrical central portion; a second domed longitudinal end having a base with a fourth outer diameter smaller than the third outer diameter; a second intermediate portion located between the generally cylindrical central portion and the second dome-shaped longitudinal end, connecting the second longitudinal end of the generally cylindrical central portion to a base of the second dome-shaped longitudinal end; the second domed longitudinal end of the liner has a dome profile that is less concave toward the interior fluid storage chamber than the domed longitudinal end having a geodesic dome profile; the pressure vessel further comprising a second dome reinforced shell having a shape complementary to both the second dome shaped longitudinal end and the second intermediate portion of the liner, said second dome reinforced shell mating with both the second dome shaped longitudinal end and the second intermediate portion of the liner; An outer composite structure seals or encases the liner and two dome reinforced shells; It is a pressure vessel.

[0034] In this configuration, each longitudinal end of the generally cylindrical central portion of the liner has a domed longitudinal end which exhibits the advantageous mechanical properties of the present invention.

[0035] Advantageously, the third outer diameter is substantially equal to the first outer diameter.

[0036] Preferably, the fourth outer diameter is approximately equal to the second outer diameter.

[0037] Advantageously, the shape of the second intermediate portion of the liner has an outer circumferential surface selected from the group consisting of a cylindrical shape, a frusto-conical shape, a curved shape, and combinations thereof.

[0038] Thus, the outer surface of the liner with the second dome reinforced shell is particularly smooth, which improves the attachment of the outer composite structure and reduces the stress levels within the pressure vessel.

[0039] Preferably, the outer circumferential surface of the second intermediate portion is a combination of a second frustoconical surface and a second cylindrical surface.

[0040] The liner may therefore be considered a stepped liner with a second tapered outer shoulder between a generally cylindrical central portion and a second dome-shaped longitudinal end.

[0041] Advantageously, the angle formed between the second frustoconical surface and the second cylindrical surface of the second intermediate portion is less than 15°, preferably less than 10°.

[0042] The angle allows for a smooth transition from the second frustoconical surface to the second cylindrical surface of the second intermediate portion and avoids the formation of sharp edges that could damage the outer composite structure. The angle also allows for reduced stresses in the tip region of the second dome reinforced shell inside the liner.

[0043] Advantageously, the angle formed between the second frustoconical surface and the outer circumferential surface of the substantially cylindrical central portion is less than 15°, preferably less than 10°.

[0044] This angle provides a smooth transition from the second frustoconical surface to the outer periphery of the generally cylindrical central portion and avoids the formation of sharp edges that could damage the outer composite structure. Additionally, when the second intermediate portion includes a second tapered outer shoulder for receiving the tip of the second dome reinforced shell, this angle reduces stresses in the tip region of the second dome reinforced shell within the liner.

[0045] Preferably, the maximum distance between the dome contour of the second dome-shaped longitudinal end and the dome contour of the dome-shaped longitudinal end having a geodesic dome contour is comprised between 0.1% and 5% of the third outer diameter, preferably between 0.5% and 2.5% of the third outer diameter.

[0046] These values ​​are suitable for the second dome-shaped longitudinal end and are easily implemented in the manufacture of the liner, allowing for a better reduction in stresses in the outer composite structure that encloses or encases the liner and the second dome-reinforced shell, which in turn allows for less composite structure to be used.

[0047] In another embodiment, the pressure vessel further comprises a hoop layer wrapped around the generally cylindrical central portion of the liner, whereby the third outer diameter includes the hoop layer.

[0048] This configuration allows the liner to be a conventional liner rather than a stepped liner, which is a liner that does not have a step.

[0049] According to the invention there is also provided a vehicle comprising a pressure vessel as described above.

[0050] Other features and advantages will become apparent from reading the following description, given by way of illustrative and non-limiting example, in conjunction with the accompanying drawings, in which: [Brief description of the drawings]

[0051] [Figure 1] 1 is an external view of a vehicle according to the present invention; [Diagram 2] FIG. 1 is a cross-sectional view of a pressure vessel according to a first embodiment of the present invention. [Figure 3A] 3 is a simulation graphic comparing differential internal stress distribution within the dome-stiffened shell of the pressure vessel of FIG. 2 and the dome-stiffened shell of the prior art in the first layer of the dome-stiffened shell; [Figure 3B] 3 is a simulation graphic comparing differential internal stress distribution within the dome-stiffened shell of the pressure vessel of FIG. 2 and the dome-stiffened shell of the prior art in the second layer of the dome-stiffened shell; [Figure 4] 3 is a simulation graphic comparing differential internal stress distribution within the outer composite structure of the pressure vessel of FIG. 2 and the outer composite structure of the prior art. [Diagram 5] FIG. 4 is a cross-sectional view of a pressure vessel according to a second embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0052] The present invention will be described with respect to certain embodiments and with reference to certain drawings, but the present invention is not limited to the embodiments and drawings, but only by the claims. The drawings described are only schematic and non-limiting. In the drawings, the size of some elements may be exaggerated and not drawn to scale for illustrative purposes. The dimensions and relative dimensions do not correspond to the actual reduction to which the invention is put.

[0053] It should be noted that the term "comprises" used in the claims should not be interpreted as being limited to the means listed thereafter, and does not exclude other elements or steps. Thus, the term should be interpreted as referring to the presence of the features, integers, steps, or components referred to and described, but does not exclude the presence or addition of one or more other features, integers, steps, or components, or groups thereof. Thus, the scope of the expression "a device comprising means A and means B" should not be limited to a device consisting only of components A and B. This expression means that in the context of the present invention, the relevant components of the device are only A and B.

[0054] FIG. 1 represents a vehicle 2 equipped with a pressure vessel 4, 4' configured to contain a gas under high pressure. For example, the pressure vessel 4, 4' may contain dihydrogen for driving a fuel cell of the vehicle. The expression "pressure vessel" means a vessel intended for storing gas under pressure and capable of withstanding an internal pressure of up to 700 bar. For example, the pressure vessel may comply with Addendum 133-Regulation No. 134 of the "Agreement Concerning the Adoption of Uniform Technical Prescriptions for Wheeled Vehicles, Equipment and Parts which can be Fitted and / or be Used on Wheeled Vehicles and the Conditions for Reciprocal Recognition of Approvals Granted on the Basis of these Prescriptions" issued by the United Nations.

[0055] FIG. 2 depicts one half of a pressure vessel 4 according to a first embodiment of the present invention. The pressure vessel 4 comprises a liner 6 that defines a fluid storage chamber 3 of the pressure vessel 4. The liner 6 has a generally cylindrical central portion 8 that defines a longitudinal axis 10 and two similar dome-shaped longitudinal ends, a first dome-shaped longitudinal end 12 and a second dome-shaped longitudinal end (only the first dome-shaped longitudinal end 12 is shown in FIG. 2). The liner 6 has a plane of symmetry that is perpendicular to the longitudinal axis 10 and passes through the center of the volume of the liner 6. In other embodiments, the liner may have only one dome-shaped longitudinal end 12.

[0056] In the following, only the first domed longitudinal end 12 will be described, since it has been found that the second domed longitudinal end can be deduced by symmetry relative to the symmetry plane, and the same applies to the first intermediate portion 13.

[0057] The generally cylindrical central portion 8 has a first outer diameter D1 at the first longitudinal end 8a of the liner 6. The first dome-shaped longitudinal end 12 has a central axis coaxial with the longitudinal axis 10 and a base portion 12a of a second outer diameter D2. D2 is smaller than D1. The liner 6 further comprises a first intermediate portion 13 located between the generally cylindrical central portion 8 and the first dome-shaped longitudinal end 12. The first intermediate portion 13 connects the first longitudinal end 8a of the generally cylindrical central portion 8 to the base portion 12a of the first dome-shaped longitudinal end 12.

[0058] In this embodiment, the first intermediate portion 13 of the liner 6 has an outer circumferential surface consisting of a combination of a first frustoconical surface 9 and a first cylindrical surface 11. The angle γ formed between the first frustoconical surface 9 and the first cylindrical surface 11 of the first intermediate portion 13 is less than 15°, preferably less than 10°. This angle corresponds to the inclination of the first frustoconical surface 9 relative to the first cylindrical surface 11, allowing a smooth transition between the two portions, thereby avoiding the formation of sharp edges. Furthermore, the angle σ formed between the first frustoconical surface 9 and the outer circumferential surface of the substantially cylindrical central portion 8 is less than 15°, preferably less than 10°. This angle corresponds to the inclination of the first frustoconical surface 9 relative to the outer circumferential surface of the substantially cylindrical central portion 8, allowing a smooth transition between the two portions, thereby avoiding the presence of sharp edges.

[0059] The first domed longitudinal end 12 of the liner 6 has a dome contour that is less concave towards the internal fluid storage chamber 3 than a domed longitudinal end having a geodesic dome contour, such as the domed longitudinal end described in US Pat. No. 5,399,433. It is provided that the maximum distance between the dome contour of the first domed longitudinal end and the dome contour of the domed longitudinal end having a geodesic dome contour is comprised between 0.1% and 5% of the first outer diameter D1, preferably between 0.5% and 2.5% of the first outer diameter D1.

[0060] The pressure vessel 4 includes a boss 14 for injecting fluid into and expelling fluid from the liner 6. The boss 14 fits into a hole located at the first domed longitudinal end 12 of the liner 6.

[0061] The pressure vessel 4 comprises a first dome-shaped reinforced shell 16 fitted onto the first dome-shaped longitudinal end 12 of the liner 6. In this embodiment, the pressure vessel 4 comprises two similar dome-shaped reinforced shells, each fitted onto one dome-shaped longitudinal end of the liner 6, the two dome-shaped reinforced shells being symmetrical to each other with respect to the above-mentioned plane of symmetry. Since it is known that the second dome-shaped reinforced shell can be deduced by the symmetry with respect to the plane of symmetry, in the following only the first dome-shaped reinforced shell 16 will be described. In this embodiment, the difference in diameter between the first outer diameter D1 and the second outer diameter D2 is such that an insertion area in the form of a first tapered outer shoulder is formed in the first intermediate portion 13 so that the first dome-shaped reinforced shell 16 is located flush with the liner 6. In this position, the first tapered outer shoulder receives the tip 27 of the first dome-shaped reinforced shell 16.

[0062] The pressure vessel 4 includes an outer composite structure 20 that encloses or encases the liner 6 and the first dome reinforced shell 16. Such outer composite structures 20 are well known in the manufacture of pressure vessels, and the outer composite structure 20 will not be described further in the following description.

[0063] The first dome reinforced shell 16 consists of a winding of layers of fiber reinforced composite material. The fiber reinforced composite material may be pre-impregnated and braided and then cured, or may not be pre-impregnated and may be impregnated, for example, by a resin infusion process or a resin transfer molding process, commonly referred to as an RTM process. During such a process, the curing of the composite material is carried out while it remains inside the resin infusion tool or resin transfer mold. It should be noted that the RTM process makes it possible to obtain a particularly smooth outer surface of the first dome reinforced shell 16 while reducing internal stresses. The first dome reinforced shell 16 has a dome-shaped portion 22 that includes a base 24 and a central axis that is coaxial with the longitudinal axis 10 of the liner 6. In this embodiment, the first dome reinforced shell 16 has a shape that is complementary to the shape of both the first dome-shaped longitudinal end 12 and the first intermediate portion 13 of the liner 6. The first dome reinforced shell 16 therefore also has a dome profile that is less concave towards the internal fluid storage chamber 3 than a dome reinforced shell having a geodesic dome profile. A first domed reinforcing shell 16 is fitted over both the first domed longitudinal end 12 and the first intermediate portion 13 of the liner 6 .

[0064] 3A and 3B show a simulation in the software ABAQUS comparing the stresses in the first dome reinforced shell 16 with the stresses in the dome reinforced shell proposed by the prior art patent document 1 cited in the preamble, in the first and second layers of fiber reinforced composite material of the first dome reinforced shell 16 and the prior art dome reinforced shell, respectively.

[0065] FIG. 4 shows a simulation in the software ABAQUS comparing the stresses in the proximal layers of the outer composite structure 20 with the stresses in the proximal layers of a prior art outer composite structure.

[0066] Figures 3A, 3B and 4 show the membrane stress in the fiber direction within the filaments, corresponding to the output UVARM8 in the simulation. In these three figures, the dotted line 28 corresponds to the evolution of the stress in the first dome reinforced shell 16 or in the outer composite structure 20 of the pressure vessel according to the invention, and the solid line 30 corresponds to the evolution of the stress in the dome reinforced shell or in the outer composite structure of a pressure vessel according to the prior art, where the domed longitudinal end of the liner has a geodesic dome profile.

[0067] Figures 3A, 3B and 4 show two improvements resulting from the invention. First, the stress in the layer of fiber-reinforced composite material of the first dome-reinforced shell 16 is reduced along the fiber by about 500 MPa (see Figures 3A and 3B). It can be seen that for the first layer, in the case of the domed longitudinal end 12 with a non-geodesic dome profile, the stress is reduced along the fiber, and in the case of the domed longitudinal end with a geodesic dome profile, the stress is slightly increased. Second, the stress in the outer composite structure 20 is also reduced by about 500 MPa to 1000 MPa in function of the position along the fiber, the invention making it possible to smooth the evolution of the stress along the fiber, thus eliminating zones of stress concentration that could possibly destroy the pressure vessel. Such destruction generally occurs after continuous pressure cycling, for example, from 20 bar to 700 bar.

[0068] Due to these advantages, it is possible to use fewer fibers in the outer composite structure 20 while maintaining the same mechanical properties for the pressure vessel. The resulting pressure vessel is lighter and requires less manufacturing time.

[0069] 5 shows an alternative embodiment of the invention in which a hoop layer 15 is wrapped around the generally cylindrical central portion 8 of the liner 6 such that the first outer diameter D1 includes the hoop layer 15.

[0070] The pressure vessel of the present invention may be manufactured by means already known in the art and will not be described further herein.

[0071] The above-described embodiments are exemplary and not restrictive. Obviously, many modifications and variations of the present invention are possible in light of the above teachings without departing from the inventive concept. It is therefore to be understood that the present invention may be practiced otherwise than as described. [Explanation of symbols]

[0072] 2 Vehicles 3. Internal Fluid Storage Chamber 4, 4' Pressure vessel 6. Liner 8 Center part of liner 6 8a first longitudinal end of central portion 8 9 First truncated cone surface 10 Longitudinal Axis 11 First cylindrical surface 12 first dome-shaped longitudinal end of liner 6 12a Base of first dome-shaped longitudinal end 12 13 first intermediate portion of central liner 6 14 Boss 15 Hoop Layer 16 First Dome Reinforced Shell 20 External composite structure 22 dome-shaped portion of first dome reinforced shell 16 24 Base of dome-shaped portion 22 27 Tip of First Dome Reinforced Shell 16 28 Dotted Line 30 Solid line

Claims

1. A pressure vessel (4, 4') A liner (6) defining an interior fluid storage chamber (3), a generally cylindrical central portion (8) having a first outer diameter D1 at a first longitudinal end (8a); a first domed longitudinal end (12) having a base (12a) of a second outer diameter D2, said second outer diameter D2 being smaller than said first outer diameter D1; a first intermediate portion (13) located between said generally cylindrical central portion (8) and said first dome-shaped longitudinal end portion (12) and connecting said first longitudinal end portion (8a) of said generally cylindrical central portion (8) to said base (12a) of said first dome-shaped longitudinal end portion (12); a liner (6), the first domed longitudinal end (12) of the liner (6) having a dome profile that is less concave toward the internal fluid storage chamber (3) than a domed longitudinal end having a geodesic dome profile; a first dome reinforced shell (16) having a shape complementary to the shapes of both the first dome-shaped longitudinal end (12) and the first intermediate portion (13) of the liner (6), the first dome reinforced shell (16) being fitted to both the first dome-shaped longitudinal end (12) and the first intermediate portion (13) of the liner (6); Boss (14) and an outer composite structure (20) that encloses or encapsulates said liner (6) and said first dome reinforced shell (16); Equipped with A pressure vessel (4, 4'), wherein the maximum distance between the dome outline of the first dome-shaped longitudinal end (12) and the dome outline of the dome-shaped longitudinal end having a geodesic dome outline is comprised between 0.1% and 5% of the first outer diameter D1.

2. 2. The pressure vessel (4, 4') of claim 1, wherein the first dome reinforced shell (16) has a dome profile that is less concave toward the internal fluid storage chamber (3) than a dome reinforced shell having a geodesic dome profile.

3. 3. The pressure vessel (4, 4') according to claim 1 or 2, wherein the first intermediate portion (13) of the liner (6) has an outer circumferential surface selected from the group consisting of a cylindrical shape, a frustoconical shape, a curved shape, and combinations thereof.

4. 4. The pressure vessel (4, 4') according to claim 3, wherein the outer peripheral surface of the first intermediate portion (13) is a combination of a first frustoconical surface (9) and a first cylindrical surface (11).

5. 5. The pressure vessel (4, 4') according to claim 4, wherein the angle γ formed between the first frustoconical surface (9) and the first cylindrical surface (11) of the first intermediate portion (13) is less than 15°.

6. 6. The pressure vessel (4, 4') according to claim 4 or 5, wherein an angle σ formed between the first frustoconical surface (9) and an outer circumferential surface of the substantially cylindrical central portion (8) is less than 15°.

7. 7. The pressure vessel (4, 4') according to any one of claims 1 to 6, further comprising a hoop layer (15) wrapped around the generally cylindrical central portion (8) of the liner (6), whereby the first outer diameter D1 includes the hoop layer (15).

8. The liner (6) is a third outer diameter at a second longitudinal end of the generally cylindrical central portion (8) opposite the first longitudinal end (8a); and a second domed longitudinal end having a base with a fourth outer diameter smaller than the third outer diameter; a second intermediate portion located between the generally cylindrical central portion (8) and the second dome-shaped longitudinal end portion and connecting the second longitudinal end portion of the generally cylindrical central portion (8) to the base of the second dome-shaped longitudinal end portion; the second domed longitudinal end of the liner (6) has a dome profile that is less concave toward the internal fluid storage chamber than a domed longitudinal end having a geodesic dome profile; The pressure vessel further comprises a second dome reinforced shell having a shape complementary to the shape of both the second dome shaped longitudinal end and the second intermediate portion of the liner (6), the second dome reinforced shell being fitted to both the second dome shaped longitudinal end and the second intermediate portion of the liner (6); The pressure vessel (4, 4') according to any one of claims 1 to 7, wherein the outer composite structure (20) seals or encases the liner (6) and the two dome reinforced shells.

9. The pressure vessel (4, 4') according to claim 8, wherein said third outer diameter is substantially equal to said first outer diameter D1.

10. The pressure vessel (4, 4') according to any one of claims 8 and 9, wherein the fourth outer diameter is substantially equal to the second outer diameter D2.

11. 11. The pressure vessel (4, 4') according to any one of claims 8 to 10, wherein the second intermediate portion of the liner (6) has an outer circumferential surface selected from the group consisting of a cylindrical shape, a frustoconical shape, a curved shape, and combinations thereof.

12. 12. The pressure vessel (4, 4') according to claim 11, wherein the outer circumferential surface of the second intermediate portion is a combination of a second frustoconical surface and a second cylindrical surface.

13. 13. The pressure vessel (4, 4') according to claim 12, wherein an angle formed between the second frustoconical surface and the second cylindrical surface of the second intermediate portion is less than 15°.

14. 14. The pressure vessel (4, 4') according to any one of claims 12 and 13, wherein an angle formed between the second frustoconical surface and an outer circumferential surface of the generally cylindrical central portion (8) is less than 15°.

15. 15. The pressure vessel (4, 4') according to any one of claims 8 to 14, wherein a maximum distance between a dome outline of the second dome-shaped longitudinal end and a dome outline of the dome-shaped longitudinal end having a geodesic dome outline is comprised between 0.1% and 5% of the third outer diameter.

16. 16. The pressure vessel (4,4') of any one of claims 8 to 15, further comprising a hoop layer (15) wrapped around the generally cylindrical central portion (8) of the liner (6), whereby the third outer diameter includes the hoop layer (15).

17. A vehicle (2) comprising a pressure vessel (4, 4') according to any one of the preceding claims.

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