Pressure vessels

Abstract

A pressure vessel includes front and rear end plates and a plurality of open-ended vessel structures constructed of fibre-reinforced polymer matrix composite material positioned adjacent to one another so that their longitudinal axes are parallel to a longitudinal direction extending between the front and rear end plates. The vessel also includes an outer reinforcement comprising polymer matrix composite material with continuous fibres extending longitudinally around the pressure vessel to secure the front and rear end plates to the vessel structures. At least one of the vessel structures has a partially curved cross section in a plane perpendicular to its longitudinal axis, such that one or more crevices are formed between the vessel structures, running longitudinally between the front and rear end plates and the front and rear end plates are shaped to allow the outer reinforcement to at least partially fill the one or more crevices between the vessel structures.

Claims

1. A pressure vessel comprising: front and rear end plates; a plurality of open-ended vessel structures, each vessel structure constructed of fibre-reinforced polymer matrix composite material and having a longitudinal axis extending between its open ends, the open-ended vessel structures positioned adjacent to one another so that their longitudinal axes are parallel to a longitudinal direction extending between the front and rear end plates, and the open-ended vessel structures being closed by the front and rear end plates; and an outer reinforcement comprising polymer matrix composite material with continuous fibres extending longitudinally along the longitudinal direction and around the pressure vessel to secure the front and rear end plates to the vessel structures; wherein at least one of the vessel structures has a partially curved cross section in a plane perpendicular to its longitudinal axis, such that one or more crevices are formed between the vessel structures, running longitudinally along the longitudinal direction between the front and rear end plates; and wherein the front and rear end plates are shaped in a plane perpendicular to the longitudinal direction such that the outer reinforcement is at least partially filling the one or more crevices between the vessel structures.

2. The pressure vessel of claim 1, wherein the outer reinforcement comprises a layer of polymer matrix composite material.

3. The pressure vessel of claim 1, wherein the outer reinforcement completely fills the one or more crevices between the vessel structures.

4. The pressure vessel of claim 1, further comprising seals arranged between the open ends of the vessel structures and the front and rear end plates.

5. The pressure vessel of claim 4, wherein the front and rear end plates comprise a plurality of flanges, each flange extending inwards along the longitudinal direction to engage with one of the open-ended vessel structures and carry one of the seals.

6. The pressure vessel of claim 1, wherein the front and rear end plates are substantially planar.

7. The pressure vessel of claim 1, wherein at least a portion of the front and rear end plates in contact with the outer reinforcement has a cross sectional profile, in a plane parallel to the longitudinal axes of the vessel structures, that is substantially curved.

8. The pressure vessel of claim 1, wherein at least one of the front and rear end plates comprises a fluid flow path between at least one of the vessel structures and another one or more of the vessel structures.

9. The pressure vessel of claim 1, wherein at least some of the vessel structures comprise at least one flat wall in a plane perpendicular to their longitudinal axes and are oriented so as to have a flat wall in contact with another flat wall of an adjacent vessel structure.

10. The pressure vessel of claim 1, wherein at least some of the vessel structures comprise a lozenge shape in a plane perpendicular to their longitudinal axes, the lozenge shape comprising first and second parallel flat walls and curved walls connecting the first and second parallel flat walls.

11. The pressure vessel of claim 10, wherein the vessel structures are arranged side-by-side in contact with one another in the pressure vessel such that the curved walls form the crevices between the vessel structures which run longitudinally between the front and rear end plates.

12. A pressure vessel according to claim 1, comprising a further reinforcement comprising polymer matrix composite material with continuous fibres extending circumferentially around the pressure vessel.

13. A pressure vessel according to claim 1, wherein each of the vessel structures is constructed of fibre-reinforced polymer in which the fibres are oriented substantially perpendicular to the longitudinal axes of the vessel structures.

14. A method of manufacturing a pressure vessel, the method comprising: positioning a plurality of open-ended vessel structures, each constructed of fibre-reinforced polymer matrix composite material and having a longitudinal axis extending between its open ends, to be adjacent to one another so that their longitudinal axes are parallel; closing the open-ended vessel structures with front and rear end plates; wherein at least one of the vessel structures has a partially curved cross section in a plane perpendicular to its longitudinal axis such that one or more crevices are formed between the vessel structures, running longitudinally along a longitudinal direction between the front and rear end plates; and applying an outer reinforcement comprising polymer matrix composite material by winding continuous fibres to extend longitudinally along the longitudinal direction and around the pressure vessel to secure the front and rear end plates to the vessel structures, wherein the front and rear end plates are shaped in a plane perpendicular to the longitudinal direction such that the outer reinforcement his at least partially filling the one or more crevices between the vessel structures.

15. The method of claim 14, comprising: applying a further outer reinforcement comprising polymer matrix composite material by winding continuous fibres to extend circumferentially around the pressure vessel.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) One or more non-limiting examples will now be described, by way of example only, and with reference to the accompanying figures, in which:

(2) FIG. 1 shows an exploded view of a pressure vessel in accordance with an example of the present disclosure;

(3) FIG. 2 shows a front cross sectional view of the pressure vessel;

(4) FIG. 3 shows a side cross sectional view of part of the pressure vessel; and

(5) FIG. 4 is a schematic side cross sectional view of an end of the pressure vessel of FIG. 1, taken in the plane indicated by the arrows (F4) of that figure.

DETAILED DESCRIPTION

(6) FIG. 1 shows an exploded view of a pressure vessel 100 in accordance with an example of the present disclosure. The pressure vessel 100 comprises: a plurality of tubular vessel structures 2A, 2B; front and rear end plates 1A, 1B; longitudinally wound fibre overwrap 3 and hoop wound fibre overwrap 7. The vessel structures 2A, 2B are open at either end and are arranged such that their longitudinal axes lie parallel to each other. They are manufactured from carbon fibre reinforced polymer composite with a high winding angle (e.g. >80 from the longitudinal axis), such that they have high resistance to hoop stresses.

(7) In FIG. 1 it can be seen that the end plates 1A, 1B are positioned to close the open ends of each vessel structure 2A, 2B. In this example the end plates 1A, 1B have an outer profile that matches the cross section of the ends of the plurality of vessel structures 2A, 2B. The longitudinal fibre 3 is wound axially under tension around the pressure vessel 100 to hold the end plates 1A, 1B in contact with the ends of the tubes 2A, 2B such that the vessel structures are sealed closed. An elastomer seal may be positioned between each end plate 1A, 1B and the vessel structures (2A, 2B) to provide closure with greater pressure resistance. An example sealing arrangement is shown in FIG. 3.

(8) The longitudinal fibre 3 is wound such that it fills the crevices 4 between the vessel structures 2A, 2B which are formed by the curvature of the walls. This prevents the longitudinal fibre 3 from slipping off the pressure vessel 100 and is more space efficient than leaving voids, or filling the crevices 4 with non-structural material that does not contribute to the strength of the pressure vessel 100. Additionally, the crevices 4 allow for greater automation of the winding process during manufacture.

(9) Fibre 7 is also wound around the vessel in the hoop (circumferential) direction under tension, providing additional hoop strength and allowing the vessel structures 2A, 2B to be constructed with thinner walls while retaining the same level of pressure resistance. This may be wound after the longitudinal fibre 3 during manufacture, such that the crevices 4 are filled and sagging of the hoop fibre reinforced layer 7 is avoided.

(10) As is seen in FIG. 2, the plurality of tubular vessel structures comprises exterior tubes 2A and interior tubes 2B, which have different cross sectional shapes, such that the interior tube-tube interfaces 6 are substantially flat, and the exterior tube walls 8 are curved. In use, the pressure inside each of the composite vessel structures may be substantially the same, such that the hoop stresses in the inter-vessel walls 6 are substantially reduced.

(11) FIG. 3 shows a side cross section of an end portion of a pressure vessel where an end plate 1 closes an open-ended vessel structure 2. The end plate 1 is a manifold comprising an internal chamber 14 and a valve 10. An elastomeric seal 9, for example an O-ring, is arranged between the end plate 1 and the vessel structure 2. The end plate 1 has a flange 15 that extends axially into the interior of the vessel structure 2 to provide a circumferential surface carrying the elastomeric seal 9. The flange 15 includes a machined groove 12 that holds the O-ring seal 9. The composite vessel structure 2 therefore floats on the elastomer seal 9 rather than being adhesively bonded to the end plate 1. This forms a mechanical connection between the composite vessel structures and the end plates.

(12) The internal chamber 14 connects the interior of the vessel structure 2 to the other vessel structures (not shown) of the pressure vessel. This allows fluid to flow between the vessel structures such that they comprise one large volume. The valve 10 is fitted at one end of the channel 14 and is operable to control the ingress and exit of gas from the pressure vessel. The valve 10 comprises a threaded portion 11, and the end plate 1 has a similarly threaded portion to enable the valve to be secured to the end plate and to seal the internal chamber 14. The valve may further comprise one or more elastomeric seals (not shown) to provide a seal with a higher pressure resistance. During use the internal chamber 14 provides a fluid flow path between the vessel structures 2 and as a result the pressure inside each vessel structure may be equal.

(13) FIG. 4 shows schematically how the longitudinally wound fibre overwrap 3 lies along the cross-sectional profile 40 of the end plate 1 and in the crevice between vessel structures 2A, 2B. The cross-sectional profile 40 of the end plate 1 is curved and the outer edge is aligned with the outer diameter of the vessel structures 2A, 2B, such that the path followed by the fibre 3 contains no sharp angles, which could lead to wear and failure. In this example, the cross-sectional profile 40 of the end plate 1 follows a smooth curve, but it could also be chamfered, or formed of several straight sections, so long as the overall cross-sectional profile 40 contains no sharp angles, for instance angles less than 110.