Storage vessel with a liquid level sensor arrangement

Abstract

A vessel (20) for storing a liquid has an inner wall (21) and an outer wall (22). The outer wall (22) is spaced outwardly and apart from the inner wall (21) to form a vacuum space (23) located between the inner wall (21) and the outer wall (22). A liquid containment volume (24) enclosed by the inner wall (21) is configured to contain the liquid within the vessel. A liquid level sensor arrangement is configured to measure a level of the liquid, the liquid level sensor arrangement having one or more light sources 11 and one or more light detectors (12). At least one of the one or more light sources (11) or one of the one or more light detectors (12) is located in the vacuum space (23).

Description

[0001] STORAGE VESSEL WITH A LIQUID LEVEL SENSOR ARRANGEMENT

[0002] This application claims priority to Australian provisional patent application 2024903956 filed on 29 November 2024 and titled 'Storage vessel with a liquid level sensor arrangement', the entire contents of which is hereby incorporated by reference.

[0003] FIELD OF THE INVENTION

[0004] The present invention relates to a storage vessel with a liquid level sensor arrangement. More particularly, but not exclusively, it relates to a cryogenic liquid storage tank with a cryogenic liquid level sensor arrangement.

[0005] BACKGROUND OF THE INVENTION

[0006] Cryogenic liquids or cryogens are liquefied gases used in the art in their liquid state at very low temperatures. Cryogens are produced by liquefying gases, by cooling the gases until they change state from gas to liquid. Cryogenic systems are now widely used in a number of different industries as they have proven to be useful in many different processes.

[0007] Storage systems or tanks for cryogenic liquids will generally comprise an inner storage volume for the cryogenic liquid that is then surrounded with insulating material. In some cases, this insulating material can be a vacuum space containing multilayer insulation, and the inner storage volume and vacuum space are then often themselves surrounded by an outer vacuum shell.

[0008] There are several known methods for level sensing of the liquid in a storage tank. For example, approaches based on radar, ultrasonic, fibre optic, thermal, mass and capacitive tomography have been used for measuring cryogenic liquid levels in some applications.

[0009] However, these approaches have drawbacks which generally make them unsuitable for use in some cryogenic applications, such as aviation. Liquid hydrogen is a cryogenic liquid which is increasingly being considered as a fuel in aviation applications, replacing traditional kerosene aviation fuels.

[0010] None of the above approaches to liquid level sensing is an ideal solution for aviation applications where accuracy, safety, reliability and light weight are all highly important. For safety reasons it is preferable to avoid including any electrical components within the storage tank. Further, accurate cryogenic liquid level sensing is important for aviation applications as pilots must have certainty about the fill level of the cryogenic liquid tank before take-off and during flight. Existing kerosene fuelled aircraft typically use differential pressure sensing to measure the kerosene tank fill level. However, this is not viable for liquid hydrogen due to the very low density of the hydrogen, and the relatively small tank size.

[0011] It is an object of the present invention to provide a storage vessel with a liquid level sensor arrangement which overcomes or at least partially ameliorates some of the abovementioned disadvantages or which at least provides the public with a useful choice.

[0012] BRIEF DESCRIPTION OF THE INVENTION

[0013] According to a first aspect the invention broadly comprises a vessel for storing a liquid, comprising: an inner wall; an outer wall, spaced outwardly and apart from the inner wall to form a vacuum space located between the inner wall and the outer wall; a liquid containment volume enclosed by the inner wall, the liquid containment volume configured to contain the liquid within the vessel; and a liquid level sensor arrangement configured to measure a level of the liquid, the liquid level sensor arrangement comprising one or more light sources and one or more light detectors; wherein at least one of the one or more light sources or one of the one or more light detectors is located in the vacuum space.

[0014] In some configurations, at least one of the light sources is located in the vacuum space.

[0015] In some configurations, the inner wall comprises a protrusion, the protrusion protruding inwardly into the liquid containment volume from the inner wall.

[0016] In some configurations, the protrusion comprises an internal region, and the internal region of the protrusion is continuous with the vacuum space.

[0017] In some configurations, the protrusion is elongate.

[0018] In some configurations, the protrusion is tubular.

[0019] In some configurations, the protrusion is a hollow elongate shape.

[0020] In some configurations, the protrusion has a base portion located at the inner wall and a body portion extending from the base portion into the liquid containment volume. In some configurations, the protrusion comprises two base portions at opposing sides of the inner wall, the body portion extending across the liquid containment volume between the two base portions.

[0021] In some configurations, the body portion extends substantially perpendicularly to the inner wall.

[0022] In some configurations, the protrusion extends at an angle between about 0 degrees and about 90 degrees to the inner wall.

[0023] In some configurations, the protrusion extends at an angle between about 45 degrees and about 90 degrees to the inner wall.

[0024] In some configurations, the protrusion has an outer surface arranged to contact the contents (e.g. liquid or gas) of the liquid containment volume.

[0025] In some configurations, the outer surface has a generally convex shape.

[0026] In some configurations, the outer surface is arranged to contact the contents of the liquid containment volume on all circumferential sides of the protrusion.

[0027] In some configurations, at least one of the one or more light sources or the one or more light detectors are located within the internal region of the protrusion.

[0028] In some configurations, at least one of the light detectors is located in the internal region of the protrusion.

[0029] In some configurations, the vessel comprises a first protrusion and a second protrusion.

[0030] In some configurations, the first protrusion comprises at least one of the one or more light sources and the second protrusion comprises at least one of the one or more light detectors.

[0031] In some configurations, the first protrusion comprises at least one of the one or more light detectors and the second protrusion comprises at least one of the one or more light detectors.

[0032] In some configurations, the first protrusion comprises at least one of the one or more light sources; the second protrusion comprises at least one of the one or more light detectors; and the vessel further comprises a third protrusion comprising at least one of the one or more light detectors.

[0033] In some configurations, the first protrusion is located between the second and third protrusion. In some configurations, the protrusion extends from or is connected at or is continuous with the inner wall at a lower region of the vessel, and the protrusion protrudes upwards in a vertical direction.

[0034] In some configurations, the protrusion comprises a plurality of light detectors, and the light detectors are arranged such that the light detectors are located at a range of heights within the protrusion.

[0035] In some configurations, the liquid is a cryogenic liquid, the liquid level sensor arrangement is a cryogenic liquid level sensor arrangement, and the vessel is a cryogenic liquid storage tank.

[0036] In some configurations, the vessel is a fuel tank configured to contain a cryogenic liquid.

[0037] In some configurations, the vessel is a dewar vessel.

[0038] In some configurations, the vessel is configured for use on an aircraft.

[0039] In some configurations, the vacuum space comprises an insulating layer, the insulating layer surrounding the inner wall.

[0040] In some configurations, the insulating layer comprises an insulating material.

[0041] In some configurations, the inner wall comprises at least one material selected from: composites, glass fibre reinforced plastic composites, fibreglass composites, fibreglass laminates, glass polymers, fibre-reinforced plastics, or carbon fibre-reinforced plastic composites.

[0042] In some configurations, at least one of the inner wall and the outer wall comprise at least one material selected from: composites, glass fibre reinforced plastic composites, fibreglass composites, fibreglass laminates, glass polymers, fibre-reinforced plastics, or carbon fibre-reinforced plastic composites.

[0043] In some configurations, the inner wall comprises glass fibre reinforced plastic composite.

[0044] In some configurations, the outer wall comprises glass fibre reinforced plastic composite.

[0045] In some configurations, the light source is configured to emit light through the inner wall into the liquid containment volume.

[0046] In some configurations, the one or more light detectors are configured to detect the light emitted from the light source after passing into or through the inner wall. In some configurations, the light detector is configured to detect whether the level of the liquid is higher than the height at which the light detector is located.

[0047] In some configurations, the one or more light detectors are arranged at a range of heights.

[0048] In some configurations, both the one or more light detectors and the one or more light sources are located in the vacuum space.

[0049] In some configurations, the vessel comprises a plurality of light detectors, each of the plurality of light detectors located at the same height, and the liquid level sensor arrangement is configured to measure an average level of the liquid from the plurality of light detectors.

[0050] In some configurations, the inner wall comprises at least one translucent region.

[0051] In some configurations, the inner wall comprises at least one transparent region.

[0052] In some configurations, the inner wall is translucent.

[0053] In some configurations, the inner wall is transparent.

[0054] In some configurations, the outer wall is opaque.

[0055] In some configurations, the vessel is enclosed by a one or more surrounding walls, the one or more surrounding walls being opaque.

[0056] In some configurations, the one or more light detectors are cameras.

[0057] In some configurations, the cameras are configured to detect the level of the liquid in the vessel.

[0058] In some configurations, the inner wall comprises a sight glass portion, the sight glass portion comprising a tubular passageway connected at a first end to an upper region of the vessel and at a second end to a lower region of the vessel.

[0059] In some configurations, the light source is located adjacently to the sight glass portion, the sight glass portion comprises a vertical portion, and the light source emits light though the length of the vertical portion.

[0060] In some configurations, the light source is configured to emit a laser light.

[0061] According to a second aspect the invention broadly comprises, a vessel for storing a liquid comprising: a wall; a liquid containment volume enclosed by the wall, the liquid containment volume configured to contain a liquid; a protrusion protruding inwardly into the liquid containment volume from the wall; and a liquid level sensor arrangement configured to measure a level of the liquid, the liquid level sensor arrangement comprising one or more light sources and one or more light detectors; wherein the protrusion comprises at least one of the one or more light sources or one of the one or more light detectors.

[0062] In some configurations, at least one of the light detectors is located in the protrusion.

[0063] In some configurations, the vessel comprises a first protrusion and a second protrusion.

[0064] In some configurations, the first protrusion comprises at least one of the one or more light sources and the second protrusion comprises at least one of the one or more light detectors.

[0065] In some configurations, the first protrusion comprises at least one of the one or more light detectors and the second protrusion comprises at least one of the one or more light detectors.

[0066] In some configurations, the first protrusion comprises at least one of the one or more light sources; the second protrusion comprises at least one of the one or more light detectors; and the vessel further comprises a third protrusion comprising at least one of the one or more light detectors.

[0067] In some configurations, the first protrusion is located between the second and third protrusion.

[0068] In some configurations, the protrusion extends from or is connected at or is continuous with the inner wall at a lower region of the vessel, and the protrusion protrudes upwards in a vertical direction.

[0069] In some configurations, the protrusion comprises a plurality of light detectors, and the light detectors are arranged such that the light detectors are located at a range of heights within the protrusion.

[0070] Other aspects of the invention may become apparent from the following description which is given by way of example only and with reference to the accompanying drawings.

[0071] As used herein the term "and / or" means "and" or "or", or both. As used herein "(s)" following a noun means the plural and / or singular forms of the noun.

[0072] The term "comprising" as used in this specification and claims means "consisting at least in part of". When interpreting statements in this specification and claims which include that term, the features, prefaced by that term in each statement, all need to be present but other features can also be present. Related terms such as "comprise" and "comprised" are to be interpreted in the same manner.

[0073] In this specification, where reference has been made to external sources of information, including patent specifications and other documents, this is generally for the purpose of providing a context for discussing the features of the present invention. Unless stated otherwise, reference to such sources of information is not to be construed, in any jurisdiction, as an admission that such sources of information are prior art or form part of the common general knowledge in the art.

[0074] For the purpose of this specification, where method steps are described in sequence, the sequence does not necessarily mean that the steps are to be chronologically ordered in that sequence, unless there is no other logical manner of interpreting the sequence.

[0075] BRIEF DESCRIPTION OF THE DRAWINGS

[0076] The invention will now be described by way of example only and with reference to the drawings in which:

[0077] Figure 1 shows a side view of a storage vessel for a liquid and a liquid level sensor arrangement;

[0078] Figure 2 shows a side view of a storage vessel for a liquid and a liquid level sensor arrangement comprising light detectors contained in protrusions;

[0079] Figure 3 shows a close-up view of a liquid level sensor arrangement comprising a protrusion;

[0080] Figure 4 shows a side view of a storage vessel for a liquid and a liquid level sensor arrangement comprising light sources and light detectors contained in protrusions;

[0081] Figure 5 shows a side view of a storage vessel for a liquid and a liquid level sensor arrangement comprising a single protrusion;

[0082] Figure 6 shows a close-up view of a liquid level sensor arrangement comprising a protrusion;

[0083] Figure 7 shows a close-up view of a liquid level sensor arrangement comprising a protrusion;

[0084] Figure 8 shows a side view of a liquid level sensor arrangement comprising a sight glass;

[0085] Figure 9 shows a side view of a cryogenic liquid level sensor arrangement;

[0086] Figure 10 shows a side view of a storage vessel for a liquid and a liquid level sensor arrangement comprising light detectors contained in protrusions and having a single wall.

[0087] DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0088] According to various aspects of the various configurations of the present invention as illustrated in figures 1-10, there is provided a liquid level sensor arrangement for a storage vessel which will now be described. It will be appreciated that these figures illustrate the general principles of the structure and construction, and that the invention is not limited to the precise configurations illustrated.

[0089] The present invention relates to a storage vessel for a liquid, and a liquid level sensor arrangement for determining the level of, or amount of, a liquid in the vessel. In other words, the present invention relates to a liquid level sensor arrangement for a vessel.

[0090] In one configuration, as shown in Figure 1, there is a liquid level sensor arrangement 10 for a vessel 20. The liquid level sensor arrangement 10 is configured to measure the level of, or amount of, liquid 30 in the vessel 20.

[0091] As shown in Figure 1, the vessel 20 has an inner wall 21 and an outer wall 22. The inner wall 21 forms a liquid containment volume 24, within which the liquid 30 can be contained. The outer wall 22 surrounds the inner wall 21, and is spaced apart from the inner wall 21, and therefore forms a space between the inner wall 21 and outer wall 22.

[0092] In some configurations this space is a vacuum space 23 and comprises a vacuum. The vacuum may provide advantages such as vacuum insulation. Additionally, the vacuum space 23 and second (outer) wall 22 may provide advantages such as improved safety by providing redundancy in the event of a failure of the inner wall 21. This arrangement may also provide an enhanced fire rating.

[0093] In some configurations, there may be one or more additional surrounding walls surrounding the outer wall 22. There may also be additional vacuum spaces between within the spaces formed by the outer wall 22 and the additional walls. In one example, there are three walls and two vacuum spaces.

[0094] In some configurations, the entire inner wall 21 is translucent. In some configurations, the inner wall 21 is of a level of translucency such that at least some light may pass through the inner wall 21 and illuminate the contents of the liquid containment volume 24, so the level or amount of the contents may be discerned or determined visibly from outside the inner wall 21. Alternatively, rather than the entire inner wall 21 being translucent, the inner wall 21 may comprise one or more translucent regions. In some other configurations, the entire inner wall 21 is transparent. In some other configurations, the inner wall 21 may comprise one or more transparent regions. In these configurations where the inner wall 21 is transparent, it may be understood that the light easily passes through the wall to illuminate the contents of the liquid containment volume 24 for detection.

[0095] In some configurations, the inner wall 21 may be constructed from a composite, glass fibre reinforced plastic composite, glass-reinforced plastic composite, fibreglass composite, fibreglass laminate, glass polymer, fibre-reinforced plastic, carbon fibre-reinforced plastic composite, or carbon fibre-reinforced composite material. These materials are advantageous as they are light-weight, may be constructed to be translucent, and can provide high levels of thermal insulation. It should be understood that the outer wall 22 may be made of the same or similar materials, however the outer wall 22 may differ from the inner wall 21 in terms of opacity or translucency as discussed in more detail below.

[0096] In one configuration, the liquid level sensor arrangement 10 has a light source 11 and a light detector 12. In some configurations there may be more than one light source 11 and more than one light detector 12. In other configurations there may be a single light source 11 and a plurality of light detectors 12.

[0097] Both the light source 11 and light detector 12 may be located within the vacuum space 23. Alternatively, one of either the light source 11 or light detector 12 may be located within the vacuum space 23.

[0098] It can be advantageous to implement the liquid level sensor arrangement 10 within the vacuum space 23, as this avoids potential safety issues due to locating and operating electrical components within the liquid containment volume 24. Locating the liquid level sensor arrangement 10 in the vacuum space 23 also eliminates the need the pass electrical wiring, cables or components through the inner wall 21. This reduces the complexity of containing the contents of the liquid containment space 24, and will be discussed in more detail further in the description. It should be understood that a similar advantage can be achieved by locating operating electrical components external to any wall containing the liquid e.g. where the electrical components are located external to a single wall vessel.

[0099] The light source 11 may emit light through the inner wall 21 into the liquid containment volume 24, from outside the inner wall 21. A light detector 12, or more than one light detectors 12, may then detect light passing through the inner wall 21 at the same location or another location.

[0100] The light sources 11 may be mounted to the inner wall 21 or outer wall 22 via a bracket or holder. The light sources 11 may be removable from the bracket or holder for servicing. In some configurations, for example as shown in Figure 2, the light source(s) 11 is located on an inner wall 21 of the vessel 20. In these configurations, it may be advantageous to have the light sources 11 on the inner wall 21, as additional material (e.g. insulation as described later) can be introduced into the vacuum space without obstructing the light entering the liquid containment volume 24 from the light sources 11.

[0101] In some configurations, the outer wall 22 is opaque to prevent or reduce interference detected by the light detector 12 from light from sources external to the vessel 20. In other configurations, the outer wall 22 may be translucent or semi-translucent, but sufficiently opaque to reduce the intensity or amount of light that can pass through the outer wall 22 to a low enough amount that will not interfere with the liquid level sensor arrangement 10.

[0102] Additionally, by providing the vacuum space 23 and thermal insulation, the outer wall 22 prevents frost forming on the inner wall 21, which would interfere with the liquid level sensor arrangement 10. The opacity of the outer wall 22 also provides a controlled environment with respect to light, so that the operation of the light sources 11 and light detectors 12 may be optimised. In an alternative configuration, there may be one or more opaque surrounding walls which surround the vessel 20. The surrounding walls prevent light from external sources reaching the vessel 20.

[0103] In some configurations the light emitted by the light source 11 is visible light. In other configurations the light may be a laser light or laser beam. The light source 11 may be a laser, where a laser refers to a light source capable of producing a coherent beam of light. In such a configuration, the light emitted is a laser beam.

[0104] The light source 11 may be an any device capable of emitting light, for example a light-emitting diode (LED). Alternatively, an incandescent light source or a fluorescent light source may be used.

[0105] There are several examples of possible light detectors 12. In some configurations, the light detectors 12 may be photoresistors, photodiodes or phototransistors, or a combination of these. Alternatively, the light detectors 12 may be cameras.

[0106] In some configurations, the volume of the liquid containment volume 24 may be between 1 and 400 litres. In other configurations, the volume of the liquid containment volume 24 may be up to 4000 litres. In other configurations, the volume of the liquid containment volume 24 may be up to 50,000 litres. In some configurations, for example as shown in Figure 2, there may be one or more protrusions 50, which each protrude inwardly into the liquid containment volume 24. Each protrusion 50 may have an internal region 53, which may extend along part of or the full length of the protrusion 50. The internal region 53 will generally need to be large enough to contain at least one light detector 12 or light source 11.

[0107] The one or more protrusions 50 may be elongate. The one or more protrusions 50 may be tubular (e.g. a hollow elongate shape). The one or more protrusions 50 may have a base portion located at the inner wall 21 and a body portion extending from the base portion into the liquid containment volume 24. The one or more protrusions 50 may each comprise two base portions at opposing sides of the inner wall 21, the body portion extending across the liquid containment volume 24 between the two base portions. The body portion may extend substantially perpendicularly to the inner wall 21, or at an angle between about 0 degrees and about 90 degrees, optionally between about 45 degrees and about 90 degrees.

[0108] The one or more protrusions 50 may have an outer surface arranged to contact the contents (e.g. liquid or gas) of the liquid containment volume 24. The outer surface may have a generally convex shape. The outer surface may be arranged to contact the contents of the liquid containment volume 24 on all circumferential sides of the protrusion 50, such that the protrusion 50 is surrounded by or immersed in the contents.

[0109] Figure 3 shows a detail view of a protrusion 50 of a configuration of the present invention. In some configurations, for example as shown in Figures 2 and 3, the internal region 53 may be continuous with the vacuum space 23, such that the vacuum space 23 may be said to extend into the internal region 53 of the protrusion 50. It should be understood that as a result the internal region 53 may comprise a vacuum.

[0110] In some configurations, this may be achieved by the protrusion 50 being constructed as part of the inner wall 21. In other configurations, the protrusion 50 may be constructed separately to the inner wall 21, then attached to the inner wall 21 at an opening in the inner wall 21. It should be understood that the protrusions 50 may be part of the inner wall 21.

[0111] In other configurations, the protrusion 50 may not have an internal region 53 continuous with the vacuum space 23. There may be an internal region 53 of the protrusion 50 that is separate and distinct from the vacuum space 23. In other configurations, there may not be an internal region 53 within the protrusion 50, and light detectors 12 and light sources 11 may be contained within the protrusion 50. The protrusions 50 may both be positioned vertically, and extend between the upper region 26 of the inner wall 21 and a lower region 25 of the inner wall 21. The protrusions 50 may extend entirely between the upper and lower regions 26, 25 of the inner wall 21. In other configurations, the protrusions 50 only extend partway between the upper and lower regions 26, 25.

[0112] In configurations in which the protrusions 50 extend partway between the upper and lower regions 26, 25, the protrusions 50 may extend vertically downwards from the upper region 26 as shown in Figure 7, or vertically upwards from the lower region 25 as shown in Figure 6. In the configuration as shown in Figure 6, the uppermost light detector 12 at the top end of the protrusion 50 may be used to detect a maximum liquid level. For example, if the liquid level is below the uppermost light detector 12 then the maximum liquid level has not been exceeded, and if the liquid level is above the uppermost light detector 12 then the maximum liquid level has been exceeded. Similarly, in the configuration as shown in Figure 7 the lowermost light detector 12 may be used to detect a minimum liquid level. In some configurations, there may be both a protrusion 50 extending upwards and a protrusion 50 extending downwards to detect both a minimum and maximum level.

[0113] Configurations such as those described above provide the advantages of improved safety, as electrical components such as the light sources 11 and light detectors 12 are not located or operated within the liquid containment volume 24, rather the electrical components are located in the vacuum space 23.

[0114] Those skilled in the art may appreciate that there are several possible configurations whereby the light detectors 12 and light sources 11 may be located within the protrusions 50 and / or the rest of the vacuum space 23 in various ways.

[0115] In some configurations, to detect the level of liquid in the liquid containment volume 24, light is emitted from the light source 11 through the inner wall 21 into the liquid containment volume 24. When the light passes through the liquid 30 contained in the liquid containment volume 24, the liquid 30 is illuminated. As a result, a light detector 12 located at a level / height submerged in the liquid 30 will detect a different amount of light to a light detector 12 located at a level / height not submerged in the liquid 30. Hence the liquid level sensor arrangement 10 can be used to determine, or can determine, that the level of the liquid is between two such light detectors 12. In a configuration such as this, increasing the number of light detectors 12 will give a more precise resolution of liquid level measurement. In some configurations, there may be a light detector 12 positioned near the bottom of the protrusion 50 at a low liquid level height. Using this, the liquid level sensor arrangement

[0116] 10 can be configured to detect that the liquid level is too low, or is at a near empty level. Similarly, there may be light detector 12 positioned near the top of the protrusion 50 at a high liquid level height. Using this, the liquid level sensor arrangement 10 can be configured to detect that the liquid level is too high, or at an overfilled level.

[0117] In some configurations, as shown for example in Figure 2, there is one light source

[0118] 11 located in the vacuum space 23 of the vessel 20, and two protrusions 50 each comprising a plurality of light detectors 12. The protrusions 50 are both oriented vertically, and run from the inner wall 21 at a lower region 25 of the vessel 20 to the inner wall 21 at an upper region 26 of the vessel 20.

[0119] The light source 11 may be located in the upper region 26 of the vessel 20. Those skilled in the art will appreciate that the light source 11 may alternatively be located in other parts of the vacuum space 23.

[0120] There may be three light detectors 12 in each protrusion 50, spaced apart so as to cover a range of the height of the liquid containment volume 24. Alternatively there may be between 1 and 20 light detectors 12 in each protrusion 50.

[0121] Multiple protrusions 50 may be used to improve the accuracy of level sensing in situations where the vessel 20 is moving or subjected to accelerations (e.g. on an aircraft). A level of the liquid may be detected at each protrusion 50, and from those an average liquid level within the vessel 20 may be determined.

[0122] In another configuration, for example as shown in Figure 4, there is a first protrusion 50 containing one or more light sources 11, and one or more second protrusions 50 each containing one or more light detectors 12. In one example, the second protrusion 50 each contain three light detectors 12, spaced apart so as to cover a range of the height of the liquid containment volume 24. The first protrusion 50 may contain a plurality of light sources 11, such that the light is emitted along the full length of the first protrusion 50 and radially in all directions from the first protrusion 50. There may be between 1 and 20 such light sources 11 (along a single protrusion 50).

[0123] In some configurations, there is more than one second protrusion 50. In one configuration there are two second protrusions 50. The first protrusion 50 may be located centrally in the liquid containment volume 24, with the second protrusions 50 each located approximately equidistant from the first protrusion 50 towards respective ends of the inner wall 21.

[0124] In some configurations, there may be a first a second and a third protrusion 50, The first protrusion 50 may comprise one or more light sources 11, and the second and third protrusions 50 may each comprise one or more light detectors 12. In some configurations, the first protrusion 50 may be located between the second and third protrusion 50. The first protrusion 50 may be located centrally in the vessel 20, and the second and third protrusions 50 may be located outwardly of the first protrusion 50. In some configurations, the second and third protrusions 50 may be equidistant from the first protrusion 50.

[0125] In some configurations, for example as shown in Figure 8, the liquid level sensor arrangement 10 may comprise a tube attached to the inner wall 21 acting as a sight glass 60. The sight glass 60 may be a sight glass portion 60 of the inner wall 21.

[0126] The sight glass 60 may comprise a vertical portion 61, an upper connecting portion 62 and a lower connecting portion 63. The vertical portion 61 is connected at its upper end to the upper connecting portion 62 and at its lower end to the lower connecting portion 63. As well as to the vertical portion 61 of the sight glass 60, the upper connecting portion 62 is connected to the inner wall 21 at the upper region 26 of the inner wall 21, and the lower connecting portion 63 is connected to the inner wall 21 at the lower region 25.

[0127] The sight glass 60 comprises a hollow internal liquid passageway through which liquid may flow. This passageway is connected to the liquid containment volume 24 such that liquid may flow from the liquid containment volume 24 into the sight glass 60, and vice versa.

[0128] The sight glass 60 may be constructed from the same material as the rest of the vessel 20, particularly where the vessel 20 is made from a translucent material. However, in a configuration where the vessel 20 is not made from a translucent material, the sight glass 60 may be constructed from a translucent material.

[0129] In some configurations, there is a light source 11 located on or adjacent to the sight glass 60. The light source 11 may be located at an end of the vertical portion 61 of the sight glass 60, and the light source 11 be configured to emit light through the full length or some of the length of the vertical portion 61 of the sight glass 60. In some configurations, the light source 11 may be a laser, and the light may be a laser light, or in other words may be a laser beam. To achieve this, the direction in which the light is emitted may be axial to the vertical portion 61 of sight glass 60. The light detector 12 may then be located adjacent to the sight glass 60 at the opposite end of the vertical portion 61. Alternatively, there may be multiple light detectors 12 located along the length of the vertical portion 61 of the sight glass 60. The light detectors 12 may be spaced along the length of the sight glass 60.

[0130] In other configurations, there may be more than one sight glass 60. For example, there may be two sight glasses 60 as shown in Figure 5. A liquid level measurement from each sight glass 60 may be taken, then these averaged to determine a liquid level of the vessel 20.

[0131] Configurations utilising a sight glass 60 may provide useful advantages such as improved reliability of measurement by dampening waves or oscillations in the detected liquid level due motion of the vessel 20. Additionally, the further separation of electrical components from the vacuum space 23 provided by these configurations may be advantageous (for improved thermal management of devices). This separation can be achieved using fibre optic connections from external devices to light sources 11 and light detectors 12.

[0132] In some configurations, the liquid level sensor arrangement 10 is a cryogenic liquid level sensor arrangement 110 for a cryogenic liquid tank 120. The cryogenic liquid level sensor arrangement 110 is configured to measure the level of, or amount of, a cryogenic liquid 130 in the cryogenic liquid tank 120. The cryogenic liquid 130 may be liquid hydrogen.

[0133] In some applications, the cryogenic liquid tank 120 may be onboard an aircraft, and the cryogenic liquid 130 may be used as a fuel for the aircraft. There are several advantages to using the present invention in this application. An accurate and light-weight integrated level sensing system in a composite tank, suitable for the application of liquid hydrogen for aviation may be achieved. Electrical components are safely contained inside a vacuum cavity and heat input into the cryogenic space is minimised, providing a high degree of safety.

[0134] Depending on the specific application, the cryogenic liquid tank 120 may have a volume or capacity of between 1 litre and 400 litres. In some aviation applications, the cryogenic liquid tank 120 may have a capacity of up to 4000 litres. For other applications such as road and rail applications, the cryogenic liquid tank 120 may have a capacity of up to 50,000 litres.

[0135] The inner wall 21, or outer wall 22, or both, of the vessel 20 may be entirely or partially constructed from glass-fibre reinforced plastic composite (GFRP composite). This may provide advantages of light weight and thermal insulating properties. Alternatively, the walls may be constructed from composites, fibreglass composites, fibreglass laminates, glass polymers or fibre-reinforced plastics.

[0136] In some configurations, the vessel 20 may be a dewar vessel. A dewar vessel may be defined as an insulated vacuum vessel intended for storing cryogens.

[0137] In some configurations, as shown in Figure 9, the vacuum space 23 may comprise an insulating layer 127. This insulating layer 127 may be a multi-layer insulation comprising multiple layers. The insulating layer 127 may that of a plurality of microspheres known in the art of cryogenic vessels, a thick foam arrangement known in the art of cryogenic vessels and / or a multi-layer vacuum jacket insulation arrangement known in the art of cryogenic vessels, where multiple layers of insulative material(s) (such as polyester film(s), silk netting(s) and / or nylon netting(s)) are densely embedded into a vacuum annulus or jacket space between the inner wall 21 and outer wall 22.

[0138] Alternatively, the insulating layer 127 may be any other suitable thin and lightweight material known in the art providing thermal insulating properties.

[0139] The insulating layer 127 may fully surround the inner wall 21.

[0140] The vacuum space 23 minimises conduction and convection heat transfer whereas the insulating layer 127 minimises radiation heat transfer. The insulating layer 127 will typically comprise a reflective multi-layer insulation but may also be aerogel. Generally in the configurations described herein, the insulating layer 127 would be located outside of the light detector 12 so as not to impede the detection of the liquid level by the light detector 12.

[0141] In cryogenic applications in particular, it is advantageous for the liquid level sensing arrangement 10 to be located in the vacuum space 23, as the need to have electrical connections such as electrical wiring, cables or components passing through the inner wall 21 is eliminated. This means the containment of the cryogenic liquid 130 is simplified, as there are no openings in the inner wall 21 required. As cryogenic liquids 130 may be stored at extreme temperatures and pressures and can be hazardous, it is particularly advantageous to eliminate openings in the inner wall 21 in a cryogenic application. The thermal insulation of the system may also be improved by eliminating openings in the inner wall 21. This arrangement may reduce the risk of fire, or provide an improved fire rating.

[0142] In contrast, passing electrical connections through the insulating layer 127 is relatively straightforward in the configurations of the invention presently described. It is possible to pass electrical connections through overlapping layers of the insulating layer 127. With the present invention it is possible to achieve an accurate and light-weight integrated level sensing system in a composite tank that will suit application of liquid hydrogen for aviation. Electrical components are safely contained inside a vacuum cavity and heat input into the cryogenic space is minimised.

[0143] In cryogenic applications in particular, it is advantageous to have more than one protrusion 50 or sight glass 60, as this allows an average of multiple liquid level measurements to be taken. This is particularly useful as a cryogenic liquid tank 120 may be onboard an aircraft, where the movement of the cryogenic liquid tank 120 can cause the liquid to move around.

[0144] In another configuration, for example as shown in Figure 10, the inner wall may be a wall 21' and the wall may enclose a liquid containment volume 24. In such a configuration there may not be an outer wall 22 or vacuum space 23. There may be one or more light sources 11 located adjacent to the wall 21' external to the liquid containment volume 24. There may be a protrusion 50 comprising one or more light detectors 12. In some configurations, there may be two, or more than two, protrusions 50. This configuration is advantageous as it allows the level of a liquid to be measured without electrical components (light sources 11 or light detectors 12) being located in the liquid containment volume 24. Additionally, electrical connections do not need to pass through the wall 21'.

[0145] To those skilled in the art to which the invention relates, many changes in construction and widely differing embodiments and applications of the invention will suggest themselves without departing from the scope of the invention as defined in the appended claims.

[0146] This invention may also be said broadly to consist in the parts, elements and features referred to or indicated in the specification of the application, individually or collectively, and any or all combinations of any two or more of said parts, elements or features, and where specific integers are mentioned herein which have known equivalents in the art to which this invention relates, such known equivalents are deemed to be incorporated herein as if individually set forth.

Claims

CLAIMS1. A vessel for storing a liquid, comprising: an inner wall; an outer wall, spaced outwardly and apart from the inner wall to form a vacuum space located between the inner wall and the outer wall; a liquid containment volume enclosed by the inner wall, the liquid containment volume configured to contain the liquid within the vessel; and a liquid level sensor arrangement configured to measure a level of the liquid, the liquid level sensor arrangement comprising one or more light sources and one or more light detectors; wherein at least one of the one or more light sources or one of the one or more light detectors is located in the vacuum space.

2. The vessel of claim 1 wherein at least one of the light sources is located in the vacuum space.

3. The vessel of any one of the preceding claims, wherein the inner wall comprises a protrusion, the protrusion protruding inwardly into the liquid containment volume from the inner wall.

4. The vessel of claim 3, wherein the protrusion is elongate.

5. The vessel of claim 3 or 4, wherein the protrusion is tubular.

6. The vessel of any one of claims 3 to 5, wherein the protrusion has a base portion located at the inner wall and a body portion extending from the base portion into the liquid containment volume.

7. The vessel of claim 6, wherein the protrusion comprises two base portions at opposing sides of the inner wall, the body portion extending across the liquid containment volume between the two base portions.

8. The vessel of claim 6 or 7, wherein the body portion extends substantially perpendicularly to the inner wall.

9. The vessel of any one of claims 3 to 8, wherein the protrusion extends at an angle between about 0 degrees and about 90 degrees to the inner wall.

10. The vessel of claim 9, wherein the protrusion extends at an angle between about 45 degrees and about 90 degrees to the inner wall.

11. The vessel of any one of claims 3 to 10, wherein the protrusion has an outer surface arranged to contact the contents of the liquid containment volume.

12. The vessel of claim 11, wherein the outer surface has a generally convex shape.

13. The vessel of claim 11 or 12, wherein the outer surface is arranged to contact the contents of the liquid containment volume on all circumferential sides of the protrusion.

14. The vessel of any one of claims 3 to 13, wherein the protrusion comprises an internal region, and the internal region of the protrusion is continuous with the vacuum space.

15. The vessel of claim 14, wherein at least one of the one or more light sources or the one or more light detectors are located within the internal region of the protrusion.

16. The vessel of claim 15, wherein at least one of the light detectors is located in the internal region of the protrusion.

17. The vessel of any one of claims 3 to 16, wherein the vessel comprises a first protrusion and a second protrusion.

18. The vessel of claim 17, wherein the first protrusion comprises at least one of the one or more light sources and the second protrusion comprises at least one of the one or more light detectors.

19. The vessel of claim 18, wherein the first protrusion comprises at least one of the one or more light detectors and the second protrusion comprises at least one of the one or more light detectors.

20. The vessel of claim 18, wherein the first protrusion comprises at least one of the one or more light sources; the second protrusion comprises at least one of the one or more light detectors; and the vessel further comprises a third protrusion comprising at least one of the one or more light detectors.

21. The vessel of claim 20 wherein the first protrusion is located between the second and third protrusion.

22. The vessel of any one of claims 3 to 21, wherein the protrusion extends from or is connected at or is continuous with the inner wall at a lower region of the vessel, and the protrusion protrudes upwards in a vertical direction.

23. The vessel of any one of claims 3 to 22, wherein the protrusion comprises a plurality of light detectors, and the light detectors are arranged such that the light detectors are located at a range of heights within the protrusion.

24. The vessel of any one of the previous claims, wherein the liquid is a cryogenic liquid, the liquid level sensor arrangement is a cryogenic liquid level sensor arrangement, and the vessel is a cryogenic liquid storage tank.

25. The vessel of any one of the previous claims, wherein the vessel is a fuel tank configured to contain a cryogenic liquid.

26. The vessel of any one of the preceding claims, wherein the vessel is a dewar vessel.

27. The vessel of any one of the preceding claims, wherein the vessel is configured for use on an aircraft.

28. The vessel of any one of the preceding claims, wherein the vacuum space comprises an insulating layer, the insulating layer surrounding the inner wall.

29. The vessel of claim 28, wherein the insulating layer comprises an insulating material.

30. The vessel of any one of the preceding claims, wherein the inner wall comprises at least one material selected from: composites, glass fibre reinforced plastic composites, fibreglass composites, fibreglass laminates, glass polymers, fibre-reinforced plastics, or carbon fibre- reinforced plastic composites.

31. The vessel of any one of the preceding claims, wherein at least one of the inner wall and the outer wall comprise at least one material selected from: composites, glass fibre reinforced plastic composites, fibreglass composites, fibreglass laminates, glass polymers, fibre-reinforced plastics, or carbon fibre-reinforced plastic composites.

32. The vessel of claim 30, wherein the inner wall comprises glass fibre reinforced plastic composite.

33. The vessel of claim 31, wherein the outer wall comprises glass fibre reinforced plastic composite.

34. The vessel of any one of the preceding claims, wherein the light source is configured to emit light through the inner wall into the liquid containment volume.

35. The vessel of any one of the preceding claims, wherein the one or more light detectors are configured to detect the light emitted from the light source after passing into or through the inner wall.

36. The vessel of any one of the preceding claims, wherein the light detector is configured to detect whether the level of the liquid is higher than the height at which the light detector is located.

37. The vessel of any one of the preceding claims, wherein the one or more light detectors are arranged at a range of heights.

38. The vessel of any one of the preceding claims, wherein both the one or more light detectors and the one or more light sources are located in the vacuum space.

39. The vessel of any one of the preceding claims, wherein the vessel comprises a plurality of light detectors, each of the plurality of light detectors located at the same height, and the liquid level sensor arrangement is configured to measure an average level of the liquid from the plurality of light detectors.

40. The vessel of any one of the preceding claims, wherein the inner wall comprises at least one translucent region.

41. The vessel of any one of claims 1 to 39, wherein the inner wall comprises at least one transparent region.

42. The vessel of claim 40, wherein the entire inner wall is translucent.

43. The vessel of claim 41, wherein the entire inner wall is transparent.

44. The vessel of any one of the preceding claims, wherein the outer wall is opaque.

45. The vessel of any one of the preceding claims, wherein the vessel is enclosed by a one or more surrounding walls, the one or more surrounding walls being opaque.

46. The vessel of any one of the preceding claims, wherein the one or more light detectors are cameras.

47. The vessel of claim 46, wherein the cameras are configured to detect the level of the liquid in the vessel.

48. The vessel of any one of the preceding claims, wherein the inner wall comprises a sight glass portion, the sight glass portion comprising a tubular passageway connected at a first end to an upper region of the vessel and at a second end to a lower region of the vessel.

49. The vessel of claim 48, wherein the light source is located adjacently to the sight glass portion, the sight glass portion comprises a vertical portion, and the light source emits light though the length of the vertical portion.

50. The vessel of any one of claims 48 or 49, wherein the light source is configured to emit a laser light.

51. A vessel for storing a liquid comprising: a wall; a liquid containment volume enclosed by the wall, the liquid containment volume configured to contain a liquid; a protrusion protruding inwardly into the liquid containment volume from the wall; and a liquid level sensor arrangement configured to measure a level of the liquid, the liquid level sensor arrangement comprising one or more light sources and one or more light detectors; wherein the protrusion comprises at least one of the one or more light sources or one of the one or more light detectors.

52. The vessel of claim 51, wherein at least one of the light detectors is located in the protrusion.

53. The vessel of any one of claims 51 to 52, wherein the vessel comprises a first protrusion and a second protrusion.

54. The vessel of claim 53, wherein the first protrusion comprises at least one of the one or more light sources and the second protrusion comprises at least one of the one or more light detectors.

55. The vessel of claim 54, wherein the first protrusion comprises at least one of the one or more light detectors and the second protrusion comprises at least one of the one or more light detectors.

56. The vessel of claim 54, wherein the first protrusion comprises at least one of the one or more light sources; the second protrusion comprises at least one of the one or more light detectors; and the vessel further comprises a third protrusion comprising at least one of the one or more light detectors.

57. The vessel of claim 56 wherein the first protrusion is located between the second and third protrusion.

58. The vessel of any one of claims 51 to 57, wherein the protrusion extends from or is connected at or is continuous with the inner wall at a lower region of the vessel, and the protrusion protrudes upwards in a vertical direction.

59. The vessel of any one of claims 51 to 58, wherein the protrusion comprises a plurality of light detectors, and the light detectors are arranged such that the light detectors are located at a range of heights within the protrusion.

60. The vessel of any one of claims 51 to 59, wherein the protrusion is elongate.

61. The vessel of any one of claims 51 to 60, wherein the protrusion is tubular.

62. The vessel of any one of claims 51 to 61, wherein the protrusion has a base portion located at the inner wall and a body portion extending from the base portion into the liquid containment volume.

63. The vessel of claim 62, wherein the protrusion comprises two base portions at opposing sides of the inner wall, the body portion extending across the liquid containment volume between the two base portions.

64. The vessel of claim 62 or 63, wherein the body portion extends substantially perpendicularly to the inner wall.

65. The vessel of any one of claims 59 to 64, wherein the protrusion extends at an angle between about 0 degrees and about 90 degrees to the inner wall.

66. The vessel of claim 65, wherein the protrusion extends at an angle between about 45 degrees and about 90 degrees to the inner wall.

67. The vessel of any one of claims 59 to 66, wherein the protrusion has an outer surface arranged to contact the contents of the liquid containment volume.

68. The vessel of claim 67, wherein the outer surface has a generally convex shape.

69. The vessel of claim 67 or 68, wherein the outer surface is arranged to contact the contents of the liquid containment volume on all circumferential sides of the protrusion.

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