PRESSURE VESSEL WITH OPTIMIZED OUTER COMPOSITE STRUCTURE

Abstract

A pressure vessel including an internal fluid storage chamber, and an outer composite structure enclosing or encasing the internal fluid storage chamber. The outer composite structure has a thickness containing both helical layers and hoop layers of reinforcing fibers, wherein at least 20% of a combined thickness of all of the helical layers are located within a 25% innermost thickness of the outer composite structure. The internal fluid storage chamber is defined by a liner including a generally cylindrical central portion having a first outer diameter at a first longitudinal end, and a first dome-shaped longitudinal end portion having a base portion and a first intermediate portion located between the generally cylindrical central portion and the base portion for connecting the first longitudinal end of the generally cylindrical central portion to the base portion of the first dome-shaped longitudinal end portion.

Claims

1. A pressure vessel comprising: an internal fluid storage chamber; and an outer composite structure enclosing or encasing the internal fluid storage chamber, wherein the outer composite structure has a thickness comprising both helical layers and hoop layers a combined thickness of all of the helical layers are located within a 25% innermost thickness of the outer composite structure, and wherein the internal fluid storage chamber is defined by a liner comprising: a generally cylindrical central portion having a first outer diameter at a first longitudinal end, and a first dome-shaped longitudinal end portion having a base portion and a first intermediate portion located between the generally cylindrical central portion and the base portion for connecting the first longitudinal end of the generally cylindrical central portion to the base portion of the first dome-shaped longitudinal end portion, wherein the pressure vessel further comprises a first dome reinforcement shell having a shape complementary to a shape of the first dome-shaped longitudinal end portion and the first intermediate portion, wherein said first dome reinforcement shell being fitted on the liner only on the first dome-shaped longitudinal end portion and the first intermediate portion.

2. The pressure vessel according to claim 1, wherein the first dome reinforcement shell flushes with the liner.

3. The pressure vessel according to claim 1, wherein at least 30% of the combined thickness of all of the helical layers are located within the 20% innermost thickness of the outer composite structure.

4. The pressure vessel according to claim 1, wherein the base portion is of a second outer diameter, the second outer diameter being smaller than the first outer diameter.

5. The pressure vessel according to claim 1, wherein the first dome-shaped longitudinal end portion of the liner has a dome contour portion which is less concave toward the internal fluid storage chamber than a dome-shaped longitudinal end portion having a geodesic dome contour portion.

6. The pressure vessel according to claim 5, wherein a greatest distance between the dome contour portion of the first dome-shaped longitudinal end portion and the dome contour portion of a dome-shaped longitudinal end portion having a geodesic dome contour portion is comprised between 0.1% and 5% of the first outer diameter.

7. The pressure vessel according to claim 1, wherein the first dome reinforcement shell has a dome contour portion which is less concave toward the internal fluid storage chamber than a dome reinforcement shell having a geodesic dome contour portion.

8. The pressure vessel according to claim 1, wherein the first intermediate portion of the liner has an outer peripheral surface selected from the group consisting of cylindrical, frustoconical, curved and combinations thereof.

9. The pressure vessel according to claim 8, wherein the outer peripheral surface of the first intermediate portion is a combination of a first frustoconical surface and a first cylindrical surface.

10. The pressure vessel according to claim 1, wherein the first dome reinforcement shell consists of a winding of layers of a fiber-reinforced composite material.

11. The pressure vessel according to claim 1, wherein the liner further comprises: a third outer diameter at a second longitudinal end, axially opposite to the first longitudinal end, of the generally cylindrical central portion, a second dome-shaped longitudinal end portion having a base portion and a second intermediate portion located between the generally cylindrical central portion and the base portion for connecting the second longitudinal end of the generally cylindrical central portion to the base portion of the second dome-shaped longitudinal end portion, the pressure vessel further comprising a second dome reinforcement shell having a shape complementary to a shape of the second dome-shaped longitudinal end portion and the second intermediate portion, said second dome reinforcement shell being fitted on the liner only on the second dome-shaped longitudinal end portion and the second intermediate portion.

12. A vehicle comprising the pressure vessel of claim 1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0055] FIG. 1 is a general view of a vehicle according to the invention;

[0056] FIG. 2 is a cross section of a pressure vessel according to a first embodiment of the invention;

[0057] FIG. 3 is a detailed view of the portion indicated by F in FIG. 2;

[0058] FIG. 4 are simulation graphics comparing the mechanical stress in the first helical layer of the outer composite structure for different helical layer arrangements within the innermost thickness of the outer composite structure;

[0059] FIG. 5 is a partial cross-section view of a second embodiment of the invention.

DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

[0060] The present invention will be described with respect to particular embodiments and with reference to certain drawings but the invention is not limited thereto but only by the claims. The drawings described are only schematic and are non-limiting. In the drawings, the size of some of the elements may be exaggerated and not drawn on scale for illustrative purposes. The dimensions and the relative dimensions do not correspond to actual reductions to practice of the invention.

[0061] It is to be noticed that the term comprising, used in the claims, should not be interpreted as being restricted to the means listed thereafter; it does not exclude other elements or steps. It is thus to be interpreted as specifying the presence of the stated features, integers, steps or components as referred to, but does not preclude 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 B should not be limited to devices consisting only of components A and B. It means that with respect to the present invention, the only relevant components of the device are A and B.

[0062] FIG. 1 represents a vehicle 2 comprising a pressure vessel 4; 4 configured for containing a gas under high pressure. For example, the pressure vessel 4; 4 may contain dihydrogen for powering a fuel cell of the vehicle. By the expression pressure vessel, it is meant a vessel intended for storing gas under pressure able to withstand an internal pressure going up to 700 bar. For example, the pressure vessel may be compliant with Addendum 133Regulation 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.

[0063] FIG. 2 represents a half of a pressure vessel 4 according to a first embodiment of the invention. The pressure vessel 4 comprises an internal fluid storage chamber 3 defined by a liner 6. The liner 6 has a generally cylindrical central portion 8 extending along a longitudinal axis 10 and two similar dome-shaped longitudinal end portions: a first dome-shaped longitudinal end portion 12 and a second dome-shaped longitudinal end portion, only the first dome-shaped longitudinal end portion 12 being shown on FIG. 2. The liner 6 has a plane of symmetry which is perpendicular to the longitudinal axis 10 and pass through a center of volume of the liner 6. In other embodiments, the liner 6 may have only one dome-shaped longitudinal end portion 12.

[0064] In the following, only the first element of each pair of elements will be described, knowing the second one can be deduced by symmetry with respect to the plane of symmetry.

[0065] The generally cylindrical central portion 8 has a first outer diameter D1 at a first longitudinal end 8a of the liner 6. The first dome-shaped longitudinal end portion 12 has a central axis coaxial with the longitudinal axis 10 and a base portion 12a of a second outer diameter D2, D2 being smaller than D1. The liner 6, more precisely the first dome-shaped longitudinal end portion 12, further comprises a first intermediate portion 13 located between the generally cylindrical central portion 8 and the base portion 12a. 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 portion 12.

[0066] The pressure vessel 4 comprises an outer composite structure 20 enclosing or encasing both the liner 6 and a first dome reinforcement shell 16. The outer composite structure 20 comprises a dome-shaped portion 21 having a base portion 21a. The first dome reinforcement shell 16 has a shape complementary to the shape of the first dome-shaped longitudinal end portion 12 and its first intermediate portion 13. The first dome reinforcement shell 16 is fitted on the liner 6 only on the first dome-shaped longitudinal end portion 12 and its first intermediate portion 13. Indeed, 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 created in the first intermediate portion 13 such that the first dome reinforcement shell 16 flushes with the liner 6. In the latter position, the first tapered outer shoulder accommodates a tip 27 of the first dome reinforcement shell 16. Thus, the first dome reinforcement shell 16 flushes with the liner 6, more preferably with the generally cylindrical central portion 8 of the liner 6. More precisely, the outer surface of the first dome reinforcement shell 16 flushes with the outer surface of the generally cylindrical central portion 8 of the liner 6.

[0067] Advantageously, the first dome-shaped longitudinal end portion 12 of the liner 6 has a dome contour portion 12b which is less concave toward the internal fluid storage chamber 3 than a dome-shaped longitudinal end portion having a geodesic dome contour portion.

[0068] Preferably, a greatest distance between the dome contour portion 12b of the first dome-shaped longitudinal end portion 12 and the dome contour portion of a dome-shaped longitudinal end portion having a geodesic dome contour portion 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.

[0069] As the first dome reinforcement shell 16 has a shape complementary to the shape of the first dome-shaped longitudinal end portion 12 of the liner 6, the first dome reinforcement shell 16 has also a dome contour portion which is less concave toward the internal fluid storage chamber 3 than a dome reinforcement shell having a geodesic dome contour portion.

[0070] In the present embodiment, the first intermediate portion 13 of the liner 6 has an outer peripheral surface consisting in a combination of a first frustoconical surface 9 and a first cylindrical surface 11.

[0071] The pressure vessel 4 comprises a boss 14 for charging and discharging a fluid into and out of the liner 6. The boss 14 is fitted in an aperture located at the first dome-shaped longitudinal end portion 12 of the liner 6, axially opposite to the base portion 12a.

[0072] The first dome reinforcement shell 16 consists of a winding of layers of fiber-reinforced composite material. The fiber-reinforced composite material may either be pre-impregnated and cured after being laid or not be pre-impregnated and impregnated by, for example, a resin infusion process or a resin transfer molding process, commonly called a RTM process. During such processes, the curing of the composite material takes place while the composite material remains inside the resin infusion tool or the resin transfer mold. It should be noted that the RTM process permits to obtain an extra smooth outer surface of the first dome reinforcement shell 16 with decreased internal stresses. The first dome reinforcement shell 16 has a dome-shaped portion 22 with a base portion 22a and a central axis which is coaxial with the longitudinal axis 10 of the liner 6. The fibers of the fiber-reinforced composite material are fibers selected from the group consisting of carbon fibers, aramid fibers and glass fibers. Preferably, the fibers of the fiber-reinforced composite material are carbon fibers.

[0073] Moreover, glass fibers layers may be provided over the outer composite structure 20, in order to protect the reinforcing fibers of the helical layers 20a and hoop layers 20b of reinforcing fibers.

[0074] FIG. 3 shows the detailed view of the portion indicated by F in FIG. 2. The outer composite structure 20 of a pressure vessel according to the present invention has a thickness T comprising both helical layers 20a and hoop layers 20b of reinforcing fibers, wherein at least 20% of the combined thickness of all helical layers 20a are located within the 25% innermost thickness T of the outer composite structure 20. In the present embodiment, the reinforcing fibers are carbon fibers. Preferably, at least 30% of the combined thickness of all helical layers 20a are located within the 20% innermost thickness T of the outer composite structure 20. In the present embodiment, the outer composite structure comprises fifteen layers: nine helical layers 20a and six hoop layers 20b.

[0075] FIG. 4 illustrates simulation results made with ABAQUS 2017 software combined with Wound Composite Modeler (as known as WCM) for ABAQUS 2017 comparing different stresses in the outer composite structure 20 enclosing or encasing both the liner 6 and the dome reinforcement shell 16. The stresses comparison is performed in the first helical layer of the nine helical layers 20a of the outer composite structure 20, in a section between distance zero and distance 21a from the center of the volume of the liner 6, wherein distance zero corresponds to the axial position of the center of the volume of the liner 6 along the longitudinal axis 10 and distance 21a corresponds to the axial position of the base portion 21a along the longitudinal axis 10 of the pressure vessel.

[0076] In this latter figure, the continuous line 28 shows that the internal stress in the first helical layer of the outer composite structure 20 can reach 3500 MPa and more in the region of the first intermediate portion 13, near the base portion 21a, when less than 20% of the combined thickness of all nine helical layers 20a are located within the 25% innermost thickness T of the outer composite structure 20. The short-dashed line 29 shows that the internal stress in the first helical layer of the outer composite structure 20 is below 3500 MPa in the region of the first intermediate portion 13, near the base portion 21a, when at least 20% of the combined thickness of all nine helical layers 20a are located within the 25% innermost thickness T of the outer composite structure 20. The long-dashed line shows that the internal stress in the first helical layer of the outer composite structure 20 is below 2500 MPa in the region of the first intermediate portion 13, near the base portion 21a, when at least 30% of the combined thickness of all nine helical layers 20a are located within the 20% innermost thickness T of the outer composite structure 20. In this simulation, the internal stress in the first helical layer of the outer composite structure 20 is actually the lamina stress in the direction of the fiber of the first helical layer of the outer composite structure 20.

[0077] From the latter figure, it will also be seen that the internal stress in the first helical layer of the outer composite structure 20 can be significantly reduced by locating more helical layers 20a within the innermost thickness T of the outer composite structure 20.

[0078] FIG. 5 shows a variant embodiment of the invention. In this embodiment, the pressure vessel 4 differs from the pressure vessel 4 in that the first intermediate portion 13 of the liner 6 has an outer peripheral surface consisting in a curved surface.

[0079] The pressure vessel of the invention may be manufactured by means which are already well known in the art and which will not be described in further details here.

LIST OF REFERENCES

[0080] 2: vehicle [0081] 3: internal fluid storage chamber [0082] 4; 4: pressure vessel [0083] 6: liner [0084] 8: generally cylindrical central portion [0085] 8a: first longitudinal end [0086] 9: first frustoconical surface [0087] 10: longitudinal axis [0088] 11: first cylindrical surface [0089] 12: first dome-shaped longitudinal end portion of the liner [0090] 12a: base portion of the first dome-shaped longitudinal end portion [0091] 12b: dome contour portion of the first dome-shaped longitudinal end portion [0092] 13: first intermediate portion [0093] 14: boss [0094] 16: first dome reinforcement shell [0095] 20: outer composite structure [0096] 20a: helical layer [0097] 20b: hoop layer [0098] 21: dome-shaped portion of the outer composite structure [0099] 21a: base portion of the dome-shaped portion of the outer composite structure [0100] 21a: second axial position [0101] 22: dome-shaped portion of the first dome reinforcement shell [0102] 22a: base portion of the dome-shaped portion of the first dome reinforcement shell [0103] 27: tip of the first dome reinforcement shell [0104] 28: continuous line [0105] 29: short-dashed line [0106] 30: long-dashed line