Device, method, vehicle, computer program product and computer processing unit for measuring a volume of a liquid in a container

Abstract

The invention relates to an apparatus, a method, a vehicle, a computer program product and a computer processing unit for measuring a volume of a liquid in a container. A volume of a liquid (e.g., cryogenically stored liquid hydrogen) in a container (e.g., a fuel tank onboard an aircraft) is measured using an acoustic sensor (118). The container comprises a plurality of chambers (112), each chamber being arranged to contain a volume of liquid. A computer processing unit (120) processes a signal from an acoustic sensor (118) that detects sound and / or vibrations from each chamber (112) and provides an indication of the volume of liquid in the container. Such sound and / or vibration may be inherently produced in the liquid contained in the container.

Description

Technical Field

[0001] The present disclosure relates to apparatus and methods for measuring the volume of a liquid in a container. More particularly, but not exclusively, the present disclosure relates to methods of measuring the volume of liquid hydrogen in a fuel tank for an aircraft. Background Art

[0002] Embodiments of the present invention relate to a fuel tank system for a hydrogen powered aircraft. Previously, an aircraft powered by hydrogen has been proposed, an example being the aircraft proposed in the Airbus project "Cryoplane". Airbus is currently developing a hydrogen powered commercial aircraft, which is planned to be launched through the "ZEROe" research and development project in the next decade or so. Such an aircraft will generally require one or more fuel tanks for storing cryogenic liquids at very low temperatures and / or very high pressures. Hydrogen can be stored in liquid form at atmospheric pressure, at temperatures of -253°C or lower. Higher temperatures are possible, but higher pressures need to be maintained. Therefore, storing cryogenic hydrogen in a tank places certain structural and material requirements on the tank in order to maintain the necessary high pressure and / or low temperature, thereby requiring both the structural strength of the fuel tank and the thermal insulation of the fuel tank.

[0003] When hydrogen is used as a fuel, a reliable method is needed to measure the amount of liquid hydrogen in one or more fuel tanks. Because liquid hydrogen must be stored under extreme conditions, traditional fuel tank metering techniques are largely unsuitable for measuring the amount of liquid hydrogen in a container. In addition, storing liquid hydrogen in a moving vehicle requires careful consideration of how the movement of the vehicle will affect the storage of hydrogen. In order to reduce unnecessary stirring of liquid hydrogen in the fuel tank, it is preferred to divide large fuel tanks into smaller sections and / or add baffles to the fuel tank or parts of the fuel tank so as to reduce the movement of large amounts of liquid hydrogen from one part of the fuel tank to another and back again due to the movement of the vehicle. Such baffles can be introduced to reduce the effect of "sloshing" of the liquid in the tank. The introduction of baffles and / or other dividers in the fuel tank adds further complexity to the reliable measurement of the amount of liquid in the fuel tank.

[0004] The present invention seeks to alleviate one or more of the above problems. Alternatively or additionally, the present invention seeks to provide a solution to the need for reliable measurement of the volume of a liquid in a container, which may for example be used to measure the fuel level of a vehicle powered by liquefied gas stored in liquid form in a fuel tank in or on the vehicle. Summary of the invention

[0005] According to a first aspect of the present invention, a device for measuring the volume of a liquid in a container is provided. The container includes a plurality of chambers, each of which is arranged to hold a certain volume of liquid. The chamber may be elongated. The shape of the chamber is preferably tubular. A processing unit (e.g., a computer processing unit) and a plurality of sensors are provided. At least one such sensor is arranged to detect noise (whether audible sound or vibration inaudible to the human ear) from each chamber. The processing unit is configured to process signals from a plurality of sensors to provide an indication of the volume of the liquid in the container. Embodiments of the present invention may involve measuring the volume of liquid in a container in the form of a fuel tank for holding liquefied gas (e.g., liquid hydrogen). It has been found that, although indirect measurement is used, the use of a sensor that detects noise / sound / vibration from each chamber of a liquefied gas fuel tank having many such chambers can provide a surprisingly accurate indication of the amount of liquid in the fuel tank. It is particularly difficult to measure the volume of liquid hydrogen in a single chamber using a sensor that needs to be installed in situ in hydrogen (due to the temperature-pressure conditions present and its requirements for sensing equipment). In such environments, it may also be difficult to measure the location of the boundary between the gas and the liquid using conventional sensing techniques. Such techniques (using optical sensors) may not be particularly accurate where the boundary layer between the gas and the liquid is not well defined, difficult to detect accurately, and / or moves during use. Therefore, the use of indirect measurements, such as acoustic measurements, provides an effective solution for measuring the volume of liquid hydrogen within such structures, and is therefore seen as a promising solution for such embodiments of the invention, such as embodiments on hydrogen-powered aircraft.

[0006] Each chamber may be at least partially defined by an inner wall (i.e., an inner wall inside the container) that separates it from an adjacent chamber. The container may include a structural partition that divides the container into a plurality of chambers. In this case, the wall of one chamber may also form the wall of another chamber. Each chamber may have its own wall that is not shared with any other chamber. Each chamber may be in the form of a tube. A chamber may be in fluid communication with another chamber, for example, via one or more holes in the wall that originally separates the chambers from each other. The chambers may have different shapes and / or different sizes. For example, the capacity of some chambers may be less than 90% of the different chambers of the container, optionally less than 80% and possibly less than 70%.

[0007] Each chamber may include internal structure to limit the movement of liquid within the chamber (e.g., reduce sloshing), such as by allowing liquid to flow slowly from one portion of the chamber to another portion of the chamber, while limiting the rapid movement of a large amount of liquid from one portion of the chamber to another portion, such as when half full. Each chamber may include one or more plates, such as baffles. The baffles may allow liquid to flow slowly from one side of the plate to the other side. This may be achieved by the plate having holes or structures that allow such flow, or may be the result of the plate not extending across the entire height and / or width of the chamber. It will be appreciated that the presence of internal structure that divides the chamber into different regions so that the flow of liquid between the regions is altered / slowed in some way may have an impact on the accuracy of a fuel gauge that relies on measuring the depth of liquid at a given location in the chamber. It has been found that embodiments of the present invention that measure the volume of liquid in a container using a noise detection sensor can operate reliably despite the presence of such baffles, thereby providing a useful alternative to liquid metering devices that rely on depth measurement at a single location within the container.

[0008] As mentioned above, the chambers may be elongate, for example extending along an axis. The axis may be substantially horizontal when the container is in use. Each chamber may be at least 5 times longer, possibly at least 10 times longer, than the square root of its cross-sectional area (i.e. taken about a section having a normal parallel to the axis along which the chamber extends).

[0009] Ten or more chambers may be provided, for example 25 or more. In the case where the container has many separate chambers, it is possible that most chambers are completely full or completely empty, which may be relatively easily determined by the signal (for example acoustic signal) from the sensor. Therefore, the accurate measurement of the total amount of liquid in the container may depend on how many chambers are partially full and how accurately the amount of liquid in the chambers that are partially full can be determined. It is believed that the more chambers and sensors provided, the more accurate the measurement of the total amount of liquid in the chamber of the container. The processing unit and / or the sensor may be configured to provide the indication of the liquid volume in a given chamber in the form of one of the different states of a discrete number (for example, one of the three states of empty, half full and full), and preferably distinguish between ten or less states. For example, it may be such a situation that the processing unit is configured to regard a single chamber as completely full, completely empty or a set number of intermediate states in one state (the set number is at least one, but no more than five intermediate states, and optionally no more than three intermediate states). In a related embodiment, even though a relatively coarse measurement of the intermediate amount of fuel in each chamber is made on a chamber-by-chamber basis, the overall measurement of the fuel can still be sufficiently accurate, particularly when it is known that only a few chambers are different from completely empty and completely full and the measurements of the completely full and completely empty chambers will be accurate.

[0010] Each chamber may be associated with at least two sensors, for example one sensor for detecting noise / sound at each end of the chamber.

[0011] Each of the plurality of sensors may be in the form of a respective microphone (or other acoustic sensing device, such as a hydrophone, although the sensors are preferably not in direct contact with the liquid in the chamber). The noise / sound detected by the sensor may be outside the audible range of human hearing. The sensor may detect noise in the form of vibrations. In some embodiments, at least some of the plurality of sensors may be in the form of vibration sensors (i.e., not necessarily in the form of conventional microphones). The sensor may include an optical sensing element. The sensor may include an electrical sensor.

[0012] Each sensor may be located at an end of a chamber associated with the sensor. Each sensor may be located away from the interior of the chamber associated with the sensor, for example at one end or the other of the chamber, or at a different location, for example away from the chamber.

[0013] In case the sensor is positioned away from the interior of the chamber, the sound from within the chamber may be arranged to propagate to the sensor via a waveguide. For example it may be the case that the sensor is connected to the chamber or the surroundings of the chamber via a waveguide, the waveguide being used to transmit the acoustic signal from the chamber to the sensor. It may be the case that each chamber acts as a waveguide, so that the acoustic energy from within the chamber is guided to the sensor via the waveguide formed by the chamber.

[0014] The sound, noise or vibration detected by the sensor may originate from inherently existing sound, noise or vibration (not specifically generated for the sensor to detect in order to measure the volume of liquid in the container). The sound or noise or vibration inherently existing in the system may originate, for example, from the sound or vibration generated by the environment outside the container in any case (for example, engine vibration when an engine is present), or from the sound or vibration generated by the movement or changes of the liquid / gas system in each chamber of the container.

[0015] According to a second aspect of the invention, a method for measuring the volume of a liquid in a container is provided. The container may, for example, be a container according to the first aspect of the invention as described or claimed herein. The container comprises a plurality of chambers for containing liquids. The method comprises the step of converting noise from each chamber into an electrical signal. The method comprises the step of processing the electrical signal to provide an indication of the volume of the liquid in the container. The method is preferably performed during an operation of removing liquid from the container, for example when liquid (e.g., fuel) is gradually drawn out of the container and used by a platform (e.g., a vehicle) during its operation.

[0016] The step of processing the electrical signal to provide an indication of the volume of the liquid in the container includes using a signal that depends primarily on noise caused by sound and / or vibrations inherently generated by the container and / or its contents. For example, the noise may include noise caused by a phase change at the boundary layer between the liquid phase and the gas phase (e.g., a hissing sound). The noise may include noise caused by the movement of the liquid in the container (e.g., splashing and / or shaking). The noise may include noise caused by vibrations of the walls of the chamber and / or the walls of the container, which vibrations may be caused by vibrations of structures around the container. The amount of liquid in the chamber / container will affect the sound of this vibration. For example, the presence of liquid in a tube will reduce the noise.

[0017] The method of the present invention is particularly suitable for embodiments in which the liquid in the container is liquid hydrogen and the container is a fuel tank of a vehicle, such as an aircraft. The container may include an insulating layer. The container may have an insulating layer including a vacuum region.

[0018] According to a third aspect of the invention, there is provided a method of measuring the volume of liquid hydrogen in a fuel tank by measuring, using a plurality of sensors, sounds and / or vibrations inherently produced by the fuel tank and / or hydrogen contained therein and using such measurements to calculate an estimate of the amount of liquid hydrogen in the fuel tank.

[0019] In the method according to the second aspect and / or the third aspect of the present invention, other parameters can be measured and used to assist in calculating the amount of liquid in the container. Such other parameters can assist in improving the measurement accuracy of the volume of the liquid in the container. Two or more, for example three or more such additional parameters can be used in the method. The method may include using parameters related to temperature measurement. The method may include using parameters related to ambient temperature. The method may include using parameters related to the temperature inside the container. The method may include using parameters related to the temperature outside the container. The method may include using parameters related to pressure measurement. The method may include using parameters related to ambient pressure. The method may include using parameters related to the pressure inside the container. The method may include using parameters related to the pressure outside the container. The method may include using parameters related to the orientation of the container. For example, the noise generated by the liquid in the chamber when the axis of the tube is horizontal may be different from the noise generated when the tube is tilted relative to the horizontal, so that, for example, the orientation and shape of the liquid and gas components in the tube are different. In the case of using a method related to a fuel tank for an aircraft, the method may, for example, include using parameters related to the roll and / or pitch of the aircraft. The method may include using parameters related to the acceleration of the container (e.g., the magnitude of the acceleration, the direction of the acceleration and / or the rate of change of the acceleration and / or the previous value of the acceleration). The method may include using parameters related to ambient noise, which may be, for example, ambient noise detected by a separate sensor and / or microphone and / or may be a measure of expected ambient noise (not directly measured when measuring the volume of liquid in the container). The method may include using parameters related to vibrations external to the container.

[0020] While calculating the amount of liquid in the container and / or in addition to calculating the amount of liquid in the container, there can also be a step of calculating an error tolerance, such as indicating a possible tolerance and / or precision of the calculated amount of liquid. Such an error tolerance can be calculated using multiple estimates of the volume of separate parts of the container (e.g., separate chambers), wherein each separate part has its own error tolerance. The error tolerance can be calculated based at least in part on how many chambers are considered to be completely full, how many chambers are considered to be completely empty, and how many chambers are considered to be partially full.

[0021] The amount of liquid in the container can be calculated using a computer model, such as a machine learning model, such as a model generated by machine learning. Such a model can, for example, enable a computer processing unit to associate (e.g., map or otherwise associate) an acoustic feature from a container or a portion of a container (e.g., an acoustic feature measured by an acoustic sensor) with an estimated value of the liquid volume. This can be achieved by using other parameters. For example, an estimated value of the liquid volume can be determined by using a computer model, optionally by using other parameters according to the acoustic features of a container or a portion of a container (and / or the acoustic characteristics / features of a signal). An algorithm or process predetermined by test data through a machine learning process can be used to convert the features of multiple parameters (including parameters from signals detected by an acoustic sensor) into an estimated measurement value of the liquid volume. The algorithm can also be optionally calibrated using in-flight data, such as by providing a full chamber, such as a known acoustic response of a chamber known to be full when measuring in-flight.

[0022] The computer model may be implemented by a computer program product.

[0023] Therefore, the present invention also provides a computer program product, which includes instructions, which when the program is executed by a computer, causes the computer to perform the functions of the above-mentioned processing unit of the present invention and / or causes the computer to calculate an estimated value of the amount / volume of the liquid according to the method of the present invention. The computer program product can be set on the computer processing unit as part of the programming of the computer processing unit.

[0024] Embodiments of the present invention have particular application when used in vehicles having fuel tanks. Thus, these embodiments may have a fuel gauge arranged to display an indication of the amount of fuel based on a measurement of the volume of fuel calculated using the present invention. The fuel gauge may be arranged to provide an indication of the amount of fuel, and also provide an indication of the confidence and / or accuracy (or possibly accuracy) of the indication. Thus, the present invention provides, according to a fourth aspect, a vehicle comprising a fuel tank and a fuel gauge device utilizing any or all of the first to third aspects of the present invention.

[0025] Embodiments of the present invention have particular applications when used for aircraft powered at least in part by hydrogen fuel carried in liquid form in one or more fuel tanks of the aircraft. The aircraft may be in the form of a hybrid hydrogen aircraft, such as an aircraft using electricity and hydrogen energy. Electricity may be generated at least in part by using hydrogen as a fuel. The aircraft may be a passenger aircraft. The passenger aircraft preferably includes a cabin, which includes a multi-row and multi-column seat unit for accommodating a plurality of passengers. The aircraft may have a capacity of at least 20 passengers, more preferably at least 50 passengers, and more preferably more than 50 passengers. The aircraft may be a commercial aircraft, such as a commercial airliner, such as a single-aisle or double-aisle aircraft. The aircraft need not be configured to carry passengers, but may be, for example, an aircraft of equal size configured to carry cargo and / or for non-commercial use. The aircraft may have a maximum take-off weight (MTOW) of at least 20 tons, optionally at least 40 tons, and possibly 50 tons or more. The aircraft may have an operational empty weight of at least 20 tons, optionally at least 30 tons, and possibly about 40 tons or more. The aircraft may include an engine powered by hydrogen combustion through a modified gas turbine engine. In such an engine, liquid hydrogen is used as a fuel for combustion with oxygen. Alternatively or additionally, the aircraft may include one or more hydrogen fuel cells for generating electricity. This electricity may be used to supplement the gas turbine engine, whether it is powered by hydrogen or other fuels on the aircraft. The aircraft may include one or more turbofan engines for providing thrust, which are, for example, at least partially powered directly by hydrogen combustion and / or powered by electricity generated by hydrogen. The aircraft may include one or more turboprop engines for providing thrust, which are, for example, at least partially powered directly by hydrogen combustion and / or powered by electricity generated by hydrogen. The aircraft may adopt wing-body fusion, which has the advantage of being wider inside for hydrogen storage and distribution purposes. The tank for storing liquid hydrogen may be located below the wing and / or within the wing. The tank for storing liquid hydrogen may be located behind the rear pressure bulkhead.

[0026] It will of course be understood that features described with respect to one aspect of the invention may be incorporated into other aspects of the invention. For example, the method of the invention may incorporate any features described with reference to the apparatus of the invention, and vice versa. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Embodiments of the invention will now be described by way of example only with reference to the accompanying schematic drawings, in which:

[0028] Figure 1 shows a front view of an aircraft according to a first embodiment of the invention;

[0029] Figure 2A portion of a liquid hydrogen fuel tank of an aircraft of a first embodiment is shown;

[0030] Figure 3 Schematically shows Figure 2 The chamber of the fuel tank and the acoustic sensor and processing unit;

[0031] Figure 4 shows an alternative arrangement of an acoustic sensor and a chamber of a fuel tank according to a second embodiment;

[0032] Figure 5 shows a flow chart illustrating a method according to a third embodiment of the present invention; and

[0033] Figure 6 A flow chart is shown, which is used to illustrate the Figure 5 The various aspects of the method used in the training phase of machine learning. DETAILED DESCRIPTION

[0034] Embodiments of the present invention relate to a fuel gauge for measuring the volume of liquid hydrogen in a fuel tank for a hydrogen powered aircraft. Figure 1 1 and includes a fuselage 104, a wing 106 and an engine 108 arranged on the lower side of the wing 106. The fuel supplied to the engine is stored in a tank system, the location of which is not shown. Figure 1 1 , but the tank system may be in wing 106 and / or in fuselage 104 , for example.

[0035] A portion of the fuel tank 110 is Figure 2 It is shown in Figure 2 A plurality of tubular fuel chambers 112 are shown, each of which is arranged to store liquid hydrogen under pressure. Thus, the fuel tank 110 is defined by an internal structure of partition walls 114 that divide the tank 110 into a plurality of chambers 112. Each tubular chamber 112 has a wall thickness large enough to allow the chamber to safely accommodate liquid hydrogen under pressure. The space defined by each chamber is tubular in shape, having a circular cross-section. The tank may optionally include a combined reinforcing element between the walls of the tubular chambers and / or in the walls. A thermal insulation material (not shown) is provided to enclose the fuel tank.

[0036] One or more chambers may be in fluid communication with one or more other chambers of tank 110. Small holes or passages (not shown) may be provided, for example, connecting adjacent chambers, for example to allow gas to escape from the chambers as it rises and collect in a higher chamber.

[0037] The structure and / or arrangement of the tubular fuel chamber 112 in the aircraft may be in accordance with the disclosure of US 2015 / 0336680, the contents of which are incorporated herein by reference.

[0038] Figure 3 The chambers 112 of the fuel tank 110 are schematically shown, each chamber 112 being connected to two acoustic sensors 118, one at each end of the tubular chamber. Each chamber is provided with an internal baffle 116 to reduce undesirable movement or "sloshing" of the liquid hydrogen within the chamber. Given that the chamber is tubular, the chamber acts as an acoustic waveguide so that acoustic energy within the chamber is guided along the chamber and can then be detected by the acoustic sensors 118 at the ends of the chamber. Figure 3 In the diagram, four chambers can be seen, but in practice there will be many more, typically more than ten and possibly more than fifty such chambers per aircraft 100. Each acoustic sensor 118 is in the form of a microphone that detects sound in a frequency range covering at least 500 Hz to 20 kHz (i.e. above the mid-range). The frequency response of the microphone used will need to be adjusted / tuned depending on the specific application and may depend on factors such as the sound frequencies inherent in the system and the size of the chamber. Each sensor delivers a digital output (possibly via an analog output of an analog-to-digital converter 119) to a processing unit 120. The digital output represents the sound signal sensed by the sensor. In this embodiment, the sensed sound is the sound inherently present in the chamber (internal sound), which originates, for example, from liquid hydrogen moving with the tank (e.g., when liquid hydrogen splashes against the chamber wall 114 or splashes against itself, creating a "sloshing" or "splashing" noise), and / or from the noise generated when gaseous hydrogen is released from the hydrogen (and / or other noise caused by phase changes at the boundary layer of gas and liquid), and / or from other vibrations / noises inherently generated outside the tank (external sound), but these vibrations / noises can also be sensed as sound by the acoustic sensor in the tank. In other embodiments, the acoustic source signal can be emitted to generate detectable sound within the tank. In all such cases, the amount of liquid hydrogen in the tank and the amount of gaseous hydrogen in the tank will affect the sound detected by the acoustic sensor. For example, the noise generated by a completely full (or substantially full) chamber will be different from the noise generated by a half-full chamber, and the noise generated by a half-full chamber will be different from the noise generated by an empty chamber. For example, the frequency distribution of the sound from a tube may depend on the degree to which the tube is full or empty. Sloshing noise may be less in a completely empty (or completely full) tube, but an empty tube may not affect external sound / vibration the same way a full tube would. Sloshing noise may be louder in a partially full chamber, or a partially full chamber may have a more different signature than a full or empty chamber. An empty chamber may also have a unique sound signature due to external vibrations causing sound and / or vibrations in the chamber.

[0039] The processing unit 120 analyses the acoustic signals from each end of each chamber 112 and assigns, using a computer program product 121 of the processing unit, a full-scale value for the chamber and a confidence indication (which may be in the form of a percentage value indicating confidence - 100% indicating no possibility of error, while 0% indicating no confidence at all in a given value) or a possible error tolerance. Using this information about each such chamber, the total amount of liquid hydrogen in the tank 110 (all such chambers) can be calculated with an overall confidence indication. This information may be presented as a fuel level with a confidence indication given as a percentage (or one of a finite number of possible confidence levels, such as one of "high", "medium" and "low"), but is presented in this embodiment as an absolute error tolerance, which is represented as + / - 2x SD, where SD is a calculated standard deviation obtained by combining the individual estimated standard deviations representing the possible error in the individual fuel level estimates for each respective chamber. The calculated fuel volume and / or optional confidence level may then be communicated to a display meter 123 which displays an indication of the amount of fuel remaining and / or optionally a confidence level based on the measurements made by the present invention. The processing unit 120 may calculate the total volume of fuel using an algorithm and / or a fuel tank model developed via machine learning. Figure 5 and Figure 6 The illustrated third embodiment describes this option in more detail.

[0040] Figure 4 An alternative arrangement of the sensor 218 relative to the fuel chamber 212 according to the second embodiment is shown. The main differences between the second embodiment and the first embodiment will now be described. Instead of placing the acoustic sensor 218 at the end of the fuel chamber 212, the acoustic waveguide 222 transmits the sound from the end of each tubular chamber 212 to the acoustic sensor 218, which is located away from the fuel tank 210 and optionally closer to the signal processing unit 220. In all other respects, the second embodiment operates in a manner similar to the first embodiment.

[0041] Figure 5A flow chart illustrating a method according to a third embodiment of the present invention is shown, which method can utilize the apparatus of the first embodiment, the second embodiment, or a different apparatus. The method is performed for a container for holding a liquid, the container comprising a number of chambers (e.g., at least 25), each chamber containing a portion of the liquid in the container. The volume of the liquid held by the container is equal to the sum of the volumes of the liquid held by the chambers. The purpose of performing the method is to measure the volume of the liquid in the container. The method includes a step 324 of converting the noise detected at each chamber into an electrical signal. A further step is performed in which a signal representing the noise from each chamber is processed 326 to provide an estimate 328 of the volume of the liquid in the container. This is done by an algorithm that estimates the volume of the liquid in the chamber for each chamber of the container. The arrangement of the container and its use in normal operation can be such that most of the chambers in the container will be completely full or completely empty, with only a few chambers being partially full. It is quite simple to determine whether a chamber is completely full, completely empty, or only partially full based on the noise generated by the chamber, as this only requires the algorithm to distinguish between three possible states. If, for example, there are 25 chambers in total, of which only 5 or fewer are likely to be partially filled, and if it is possible to confidently detect whether a chamber is in one of these three states, then the accuracy of measuring the amount of liquid in the 25 chambers will be better than + / - 10%. For example, if the algorithm considers five chambers to be absolutely empty and fifteen chambers to be absolutely full, and five chambers to be partially full, then it can be determined that the percentage of the total volume of the container that is filled with liquid must be 70% ± 10%.

[0042] The algorithm used to process these signals to indicate the volume of liquid in the container can alternatively be more accurate, so that the amount of liquid in a partially full chamber can be determined more accurately. This in turn can more accurately measure the total amount of liquid in the container. A suitable method for providing a more accurate algorithm is to use a machine learning system to generate an optimized container model, and use the optimized algorithm to convert the received data into an accurate indication of the total volume of the liquid. Figure 6 Such a method utilizing such a machine learning system 430 is shown.

[0043] The purpose of the machine learning system 430 is to output a model 432 that describes the characteristics of both the container and the environment in which the container is used in practice. For example, the container can be a liquid hydrogen fuel tank for use on an aircraft, which will experience certain vibrations, temperature changes, pressure changes, orientations, and changes in acceleration / motion during use during operation. All of these external characteristics will have an impact on the sound detected by the acoustic sensor, and in order to generate more accurate models and algorithms, these external characteristics need to be taken into account. Of course, if additional parameters are used in generating models and algorithms during the learning phase, it is expected to have additional data representing these additional parameter inputs during the use of the system. As a first step, a set of candidate variables are identified from the available data for use in the machine learning algorithm 438. In terms of the sound emitted by the liquid in the chamber of the container and its relationship to the degree of filling of the chamber, the first suitable candidate variable is to extract a measurement value from the sound ("sloshing noise") generated by the overall movement of the liquid in the container when parts of the liquid come into contact with other parts of the liquid or the inner surface of the container. This sloshing noise will vary depending on the degree of filling of the liquid in the chamber. A second suitable candidate variable is to extract a measurement of the noise generated by the phase change at the boundary layer between the liquid and the gas in the chamber, which is typically caused by the gas bubbling out of the liquid ("hiss"). This hiss will depend on various factors, including the degree of agitation of the liquid and changes in temperature and pressure within the chamber. In addition, the frequency distribution of the hiss may change as the level of liquid in the chamber changes. A third suitable candidate variable is to extract a measurement of the following noise (or vibration): the noise (or vibration) is inherently generated by the platform (in this case, the aircraft) and detected by the acoustic sensor (or vibration sensor) after passing through the liquid in the chamber. This inherent noise or vibration from the platform can have a relatively easy to understand and / or consistent frequency characteristic, and the inherent noise or vibration changes in a manner that depends on the relative volume of liquid / gas in the chamber when passing through the container and the liquid / gas in the individual chamber. These three candidate variables constitute the measured "noise" 434 of the chamber.

[0044] Other candidate variables 436 include measurements such as ambient pressure, ambient temperature, pressure and temperature measurements from various chambers of the container, orientation of the platform (e.g., orientation of the aircraft, and therefore may include measurements of aircraft pitch, aircraft roll, acceleration, etc.), measurements or predictions of ambient noise from outside the container during use, and vibrations from outside the container during use.

[0045] The model of the container 432 will include not only factors such as the number and geometry of the chambers, the internal volume of the chambers, and the extent to which the container is filled and emptied in normal use, but may also include variables such as the location of the acoustic sensor relative to the chambers, the materials and dimensions of the structures defining the chambers, and the overall structure of the container. The model 432 may also include details that depend on the platform on which the container is used, which may include expected vibrations and noise generated during standard use of the platform, etc. In some embodiments, a separate model of the container may not be provided, but rather included as part of the machine learning algorithm 438, and the selection of variables may be taken into account when training the machine learning algorithm 438.

[0046] During the learning phase, the machine learning algorithm 438 receives the noise measured by the acoustic sensor (indicated by arrow 446), all other parameters 436 (e.g., not the noise measurement), and uses the model 432 of the container and the existing algorithm to generate (indicated by arrow 448) a measurement 440 of the volume of the liquid within the container. The machine-generated measurement 440 of the volume is compared to the known volume 442 (indicated by arrows 450 and 452), so that the model 432 of the container and / or the machine learning algorithm 438 are updated and improved 444, wherein the updated information is transmitted back into the model so that the process is repeated with the updated information (indicated by arrows 454 and 456). Such a process is performed multiple times using test data so that the algorithm 438 and model 432 can be optimized according to standard machine learning techniques. After optimizing the model 432 and algorithm 438 using sufficient training data, the model 432 and algorithm 438 can then be deployed as part of software in a computer processing unit to be used, for example, in converting the noise measurement 434 and any other necessary parameters 436 into a measurement 440 of the volume of liquid within a container, such as Figure 5 as shown in the method.

[0047] Although the present invention has been described and illustrated with reference to specific embodiments, it will be appreciated by those skilled in the art that the invention lends itself to many different variations not specifically described herein. Some possible variations will now be described by way of example only.

[0048] The acoustic sensors used may have different frequency responses.

[0049] The three-dimensional shape of the tank can be shaped to fit in a part of an aircraft, such as a wing, or a part of a fuselage, and can therefore have a complex shape, which means that the length of some chambers is different from the length of other chambers. In some embodiments, the chambers can have a generally tubular shape, but can also have a cross-section in the form of a square, rectangular, hexagonal, etc. The size of some chambers can be different from the size of other chambers. For example, the arrangement can be such that the lowest 25 chambers in the fuel tank can each accommodate about 1% of the total fuel capacity of the tank, and the remaining 25 chambers (located higher) each accommodate about 3% of the total fuel capacity. This can be beneficial in the following situations: the accuracy of fuel metering is limited by distinguishing which fuel tanks are empty and which fuel tanks are full, and the accuracy of the measurement is greatly affected when the tank is close to empty. Therefore, this may enable the system to measure the fullness of the tank when it is 1 / 4 full or less with an accuracy of + / -0.5%. This can be compared with the case of 50 tubes of the same capacity, allowing measurements to be made with an accuracy of + / -1% at any given level of fullness.

[0050] Each chamber may be provided with only one acoustic sensor. In some embodiments, there may be fewer acoustic sensors than chambers if the manner in which the chambers are emptied during operation is well understood and such that a higher accuracy of the fuel level is required when the tank is near empty (and / or near full) than at another level (such as near half full).

[0051] Each sensor may be in the form of an optical sensor which outputs an optical signal in dependence on the vibration / sound detected for processing by a suitable processing unit.

[0052] Each sensor may be integrated as part of an end of the chamber, such as an end cap.The sensor or part of the sensor may form part of the structure of the chamber and / or form part of the wall of the chamber.

[0053] The volumes of other liquid fuels, liquefied gases, or cryogenic liquids may be measured using similar techniques as described above.The embodiments described may have applications in vehicles other than aircraft, and may have applications unrelated to vehicles.

[0054] In the foregoing description, when referring to an integral body or element having a known, obvious or foreseeable equivalent, such equivalent is incorporated herein as if set forth separately. The true scope of the invention should be determined by reference to the claims, which should be interpreted as including any such equivalents. The reader will also understand that integral components or features of the invention described as preferred, advantageous, convenient, etc. are optional and do not limit the scope of the independent claims. In addition, it should be understood that in some embodiments of the invention, such optional integral bodies or features, although they may be beneficial, may not be desired, and therefore may not exist in other embodiments.

[0055] Unless the context requires otherwise, the term "or" should be construed as "and / or".

Claims

1. A device for measuring the volume of a liquid in a container, wherein: The container comprises a plurality of chambers, each chamber being arranged to contain a volume of liquid, and The device comprises a processing unit and a plurality of sensors, such that at least one sensor is arranged to detect noise from each chamber, The processing unit is configured to process signals from a plurality of the sensors to provide an indication of the volume of liquid in the container.

2. The device according to claim 1, wherein: The container is a fuel tank for containing liquefied gas.

3. The device according to claim 1 or 2, wherein: Each chamber is in the form of a tube.

4. Apparatus according to any preceding claim, wherein: Ten or more chambers are provided.

5. Apparatus according to any preceding claim, wherein: Each chamber is associated with at least two sensors.

6. Apparatus according to any preceding claim, wherein: Each sensor of said plurality of said sensors is in the form of a respective microphone.

7. Apparatus according to any preceding claim, wherein: Each sensor is positioned at an end of the chamber with which the sensor is associated and / or away from the interior of the chamber with which the sensor is associated.

8. Apparatus according to any preceding claim, wherein: Each cavity acts as a waveguide such that acoustic energy from within the cavity is guided along the waveguide formed by the cavity to the sensor.

9. Apparatus according to any preceding claim, wherein: Each sensor is positioned remote from the interior of the chamber with which the sensor is associated, and sound detected by the sensor from within the chamber is propagated to the sensor via a waveguide.

10. Apparatus according to any preceding claim, wherein: The sensor is arranged to detect sounds and / or vibrations inherently generated by the fuel tank and / or a liquid or gas contained in the fuel tank.

11. A method for measuring the volume of a liquid in a container, the container comprising a plurality of chambers, the method comprising the following steps: Convert the noise from each chamber into an electrical signal, and The electrical signal is processed to provide an indication of the volume of liquid in the container.

12. The method according to claim 11, wherein: The step of processing the electrical signal to provide an indication of the volume of liquid in the container comprises using a signal generated by sensing sounds and / or vibrations inherently generated by the container and / or the contents of the container.

13. The method according to claim 12, wherein: The sounds and / or vibrations inherently generated by the container and / or the contents of the container include one or more of the following: Noise caused by phase changes at the boundary layer between the liquid and gas phases, noise caused by the movement of the liquid within the container, and Noise caused by vibrations of the walls of the chamber and / or the walls of the container.

14. The method according to any one of claims 11 to 13, wherein: The liquid in the container is liquid hydrogen, and The container is a fuel tank of a vehicle.

15. A method of measuring the volume of liquid hydrogen in a fuel tank by utilizing a plurality of sensors to measure the sound and / or vibrations inherently generated by the fuel tank and / or the hydrogen contained therein and using these measurements to calculate an estimate of the amount of liquid hydrogen in the fuel tank.

16. The method according to any one of claims 11 to 15, wherein: Other parameters are measured and used to assist in calculating the amount of liquid in the container, the other parameters comprising two or more of the following: Ambient temperature, The temperature in the container, The temperature outside the container, Environmental pressure, The pressure inside the container, The pressure outside the container, the orientation of the container, The acceleration of the container, Ambient noise, and Vibrations outside of the container.

17. The method according to any one of claims 11 to 16, wherein: The method includes calculating the amount of liquid in the container and calculating an error tolerance using a plurality of estimates of volumes of separate portions of the container, wherein each separate portion has its own error tolerance.

18. The method according to any one of claims 11 to 17, wherein: The method comprises calculating the amount of liquid in the container using a computer model, optionally using other parameters, which relates acoustic characteristics from the container or a portion of the container to an estimate of the volume of the liquid.

19. A vehicle comprising a fuel tank and a fuel gauge device for providing an indication of the volume of fuel in the fuel tank, wherein: The fuel gauge device comprises: Apparatus according to any one of claims 1 to 10, and / or wherein the fuel gauge apparatus operates using a method according to any one of claims 11 to 18.

20. The vehicle of claim 19, the vehicle being an aircraft, and wherein: The fuel tank is a liquid hydrogen fuel tank.

21. A computer program product comprising instructions which, when the program is executed by a computer, cause the computer to perform the functions of a processing unit according to any one of claims 1 to 10 and / or cause the computer to calculate an estimate of the amount / volume of a liquid according to a method according to any one of claims 11 to 18.

22. A computer processing unit programmed with a computer program product according to claim 21.

Images