Ventilation system, fueling system, method of discharging tank fluid, and non-transitory computer-readable storage medium

Abstract

The invention discloses a ventilation system, a fueling system, a method of discharging a tank fluid, and a non-transitory computer-readable storage medium. The vent system includes a vent standpipe for discharging tank fluid of the fuel tank outside the vent pipe during fueling of the fuel tank. The vent pipe includes a conduit including a conduit inlet and a conduit outlet, the conduit outlet leading to the atmosphere outside the conduit. The vent pipe also includes an opening leading to the conduit between the conduit inlet and the conduit outlet. The opening is fluidly connected or connectable to the fuel tank such that, in use, tank fluid flows from the fuel tank through the opening to the conduit outlet. The vent pipe also includes a fluid mover operable to flow a mixer fluid, which may be received in the conduit inlet, through the conduit toward the conduit outlet, thereby mixing the mixer fluid with the canister fluid in the conduit upstream of the conduit outlet.

Description

Technical Field

[0001] The present invention relates to a venting system for a fuel tank, a fuel filling system and a method of draining fluid from a fuel tank. The fuel tank may be an aircraft fuel tank. Background Art

[0002] Aircraft fuel systems typically include a fuel tank and a vent for discharging fluid from the fuel tank to the atmosphere outside the fuel tank. Such fluid may include air or gaseous fuel in the fuel tank, and the fluid may be discharged to regulate the pressure in the fuel tank. For example, when the external pressure decreases during the climb phase of the aircraft flight, the pressure in the fuel tank may be relieved by discharging fluid from the fuel tank through the vent to the atmosphere. The pressure may also be relieved during the refueling of the tank. This may release the gas in the tank to make room for the liquid fuel supplied to the tank. Summary of the invention

[0003] A first aspect of the invention provides a vent system comprising a vent duct for discharging tank fluid from a fuel tank external to the vent duct during refueling of the fuel tank. The vent duct comprises: a conduit comprising a conduit inlet and a conduit outlet, the conduit outlet leading to atmosphere external to the conduit; an opening leading to the conduit between the conduit inlet and the conduit outlet, the opening being fluidly connected or connectable to the fuel tank so that, in use, tank fluid flows from the fuel tank through the opening to the conduit outlet; and a fluid mover operable to cause a mixer fluid, which may be received in the conduit inlet, to flow through the conduit toward the conduit outlet, thereby mixing the mixer fluid with the tank fluid in the conduit upstream of the conduit outlet.

[0004] In this way, the outlet fluid discharged from the conduit outlet to the atmosphere includes a mixture of the mixer fluid and the tank fluid. Thus, the outlet fluid can include a lower concentration of the tank fluid component relative to the tank fluid received through the opening. In other words, the mixing of the mixer fluid and the tank fluid upstream of the conduit outlet dilutes the components of the tank fluid in the mixer fluid before the tank fluid is discharged into the atmosphere. This may be particularly beneficial when the component is a flammable component, such as when the tank fluid includes a fuel such as a gaseous fuel. In this case, by mixing the tank fluid with the mixer fluid upstream of the outlet to reduce the concentration of the flammable fluid, the possibility of the outlet fluid burning can be reduced when the outlet fluid is discharged into the atmosphere. This can in turn improve the safety of the vent pipe, thereby allowing the vent pipe to be positioned closer to personnel than when the tank fluid is directly discharged to the atmosphere without being mixed with the mixer fluid in the conduit upstream of the outlet.

[0005] Alternatively, the conduit inlet is open to the atmosphere outside the conduit. In this way, the mixer fluid may include the atmosphere surrounding the conduit, such as air. Therefore, the ventilation system may be configured to mix the tank fluid with air in the conduit upstream of the conduit outlet. Alternatively, the tank fluid includes a gaseous fuel from an ullage space of the fuel tank. The pressure of the gaseous fuel in the ullage space may increase as fuel is supplied to the fuel tank during refueling of the fuel tank. Therefore, the gaseous fuel may be discharged from the fuel tank via the opening and mixed with a mixer fluid, such as air, in the conduit to reduce the flammability of the fuel before the fuel is discharged into the atmosphere via the conduit outlet.

[0006] Alternatively, the fuel tank is configured to store hydrogen fuel, such as hydrogen fuel for an aircraft engine. Alternatively, the gaseous fuel is a gaseous hydrogen fuel that can easily react with oxygen in the atmosphere outside the conduit. By mixing the hydrogen fuel and air in the conduit, any initial reaction between the hydrogen fuel and the oxygen in the air also occurs in the conduit. As the hydrogen fuel and air further mix in the conduit, the concentration of the hydrogen fuel in the mixture decreases. This can provide a region in the conduit upstream of the conduit outlet where the hydrogen fuel / air mixture can burn. This can in turn provide a safer way to discharge the gaseous hydrogen fuel from the fuel tank than, for example, discharging the hydrogen fuel directly into the atmosphere outside the fuel tank.

[0007] Optionally, the cross-sectional area of ​​the opening is smaller than the cross-sectional area of ​​the conduit inlet. In this way, a larger volume flow rate can be obtained more easily through the conduit inlet than through the opening.

[0008] Optionally, the fluid propeller is a first fluid propeller, and the ventilation system includes one or more additional fluid propellers, which can be operated to cause a mixer fluid that can be received in the conduit inlet to flow through the conduit toward the conduit outlet, thereby mixing the mixer fluid with the tank fluid in the conduit upstream of the conduit outlet. Optionally, the fluid propeller includes a fan. Optionally, the additional fluid propeller or each additional fluid propeller includes a fan. Optionally, the fluid propeller is located in the conduit downstream of the conduit inlet. Optionally, the additional fluid propeller or each additional fluid propeller is located in the conduit downstream of the conduit inlet.

[0009] Optionally, the or each additional fluid propeller is configured to provide a volume flow rate that is equal to or substantially equal to the volume flow rate of the first fluid propeller described above. In this way, in the event of a failure of one of the fluid propellers, another of the fluid propellers is able to provide a volume flow rate of the mixer fluid that reduces the concentration of a component in the outlet fluid to below the lower flammable limit (LFL) of the component. This can provide improved redundancy and / or can improve the performance of the ventilation system when each of the fluid propellers is operated simultaneously.

[0010] Optionally, the vent tube comprises a geometry configured to impart turbulence into the mixer fluid upstream of the opening.Such a geometry may improve mixing of the mixer fluid in the conduit upstream of the conduit outlet.

[0011] At least a portion of the geometry is located in the conduit upstream of the opening. Optionally, the geometry is located entirely in the conduit upstream of the opening. By positioning some or all of the geometry upstream of the opening, exposure of the geometry to a mixture of mixer fluid and tank fluid in the conduit at or downstream of the outlet can be reduced or eliminated. This in turn can increase the life of the geometry, particularly when the mixture is flammable or there may be a flame in the conduit downstream of the opening.

[0012] At least a portion of the geometry may be located in the conduit downstream of the opening. By positioning at least a portion of the geometry in the conduit downstream of the opening, the geometry may continue to impart turbulence to the mixture of the mixer fluid and the tank fluid downstream of the opening, which may increase the level of mixing of the mixer fluid and the tank fluid in the conduit.

[0013] Optionally, at least a portion of the inner wall of the conduit downstream of the opening comprises a region having a higher thermal resistance than another portion of the inner wall. Optionally, at least a portion of the inner wall comprises a thermally insulating material defining the region. Optionally, the conduit comprises a thermally insulating coating or layer on the inner surface of the conduit to define the region.

[0014] The area with increased thermal resistance can allow the conduit to adapt to the flame downstream of the opening, which may occur when the (combustible) component of the tank fluid (such as hydrogen fuel) first encounters the mixer fluid (such as air). The flame in the cross-flow of the mixed fluid has a lower emissivity than the flame in the static atmosphere. Therefore, the opening is provided in the conduit so that the tank fluid is entrained in the cross-flow of the mixer fluid when in use, which can reduce the heat radiated by this flame compared with the flame generated by, for example, directly discharging hydrogen to the atmosphere outside the fuel tank. In addition, such as due to the combustion of the component, or due to the increased mixing caused by the turbulence generated by the flame, the presence of the flame in the conduit can further reduce the concentration of the components of the tank fluid in the mixture of the tank fluid and the mixer fluid in the conduit downstream of the opening. This can reduce the possibility of the presence of flame at the conduit outlet or downstream, thereby improving the safety of the vent pipe. The thermal insulation material can allow the conduit to better withstand the heat generated by this flame, thereby improving the life of the vent pipe.

[0015] As described above, the mixing of the tank fluid and the mixer fluid in the conduit can ensure that such flames only exist in the conduit area upstream of the conduit outlet and downstream of the opening, so that there is no flame at or downstream of the conduit outlet. This can improve the safety of the ventilation system. It will be understood that increasing the mixing rate of the tank fluid and the mixer fluid in any manner as described above can reduce the size of the area where such flames may exist during use, which in turn can reduce the amount of thermal insulation material provided for thermally insulating the conduit in this area. This can reduce the cost and / or weight of the ventilation pipe.

[0016] Optionally, the thermal insulation material at least partially extends circumferentially around at least a portion of the inner wall of the conduit. Optionally, the thermal insulation material extends axially along at least a portion of the inner wall of the conduit on one or both sides of the opening. Increasing the extent to which the thermal insulation material extends around the circumference of the conduit or extends axially on either side of the opening, and particularly downstream of the opening, may increase the ability of the conduit to accommodate flames in regions of the conduit upstream of the conduit outlet and downstream of the opening.

[0017] Optionally, at least a portion of the opening is at a distance from each portion of the inner wall of the conduit by an amount greater than 20% of the minimum distance between the opposing sides of the conduit. Optionally, the amount is greater than 30% of the minimum distance, such as greater than 40% of the minimum distance, such as up to 50% of the minimum distance. Optionally, the opening is substantially centrally located in the conduit.

[0018] In use, having the conduit opening away from the side of the inner wall may allow the tank fluid to flow better from the opening into the central portion of the conduit. This may improve the amount or uniformity of mixing of the tank fluid and the mixer fluid in the conduit compared to, for example, an opening located in the inner wall. This may improve the safety of the vent pipe.

[0019] Optionally, the opening leads to the conduit in a direction at least partially toward the conduit outlet. This can better ensure that the tank fluid flows along the conduit toward the conduit outlet. This in turn can provide a more stable and / or predictable flame in the conduit downstream of the outlet. Optionally, the opening is substantially aligned with the central axis of the conduit, which can further ensure that the tank fluid flows away from the opening toward the outlet. Optionally, the opening leads to the conduit in a tangential direction at least partially around the conduit. This can provide a tangential component to the tank fluid flow from the opening, thereby increasing mixing in the conduit. Optionally, the opening opens in the conduit in a substantially radial direction. In this way, the mixer fluid can provide shear forces to the tank fluid leaving the opening, which can increase mixing in the conduit.

[0020] Optionally, the opening is a first opening and the vent conduit comprises one or more further openings leading to the conduit between the conduit inlet and the conduit outlet. Optionally, the or each further opening is or can be fluidly connected to a fuel tank so that, in use, tank fluid flows from the fuel tank through the respective further opening to the conduit outlet.

[0021] Providing multiple such openings may allow tank fluid to flow to different portions of the conduit simultaneously, which may increase the rate of mixing of the tank fluid with the mixer fluid in the conduit.

[0022] Alternatively, the opening or each opening is at least partially defined by an orifice in the side wall of the conduit in the conduit. Alternatively, in use, the conduit is configured to deliver fluid from the fuel tank to the opening or to each additional opening when provided with additional openings. Alternatively, the conduit is oriented toward the conduit outlet in the axial direction of the conduit so that one or more additional openings in the additional openings are substantially radially directed to the conduit. Alternatively, when provided with additional openings, the additional opening or each additional opening is defined by a corresponding orifice in the side wall of the conduit. The conduit may include a plurality of such openings, which are spaced circumferentially and / or axially around the side wall of the conduit, such as in an array, to define the opening in the conduit and the corresponding additional openings.

[0023] Providing a plurality of such openings may allow the tank fluid to be discharged in the conduit in multiple directions simultaneously, which may improve mixing in the conduit. Providing the opening and / or one or more further openings as openings in the side wall of the conduit may also provide a simple, relatively low cost solution for conveying the tank fluid from the fuel tank to the conduit.

[0024] Optionally, the opening and / or each of the further openings may be at least partially defined by a nozzle. Optionally, the or each nozzle is configured to, in use, limit the pressure and / or increase the velocity of the tank fluid discharged from the opening into the conduit. Increasing the velocity of the discharged tank fluid may increase the rate of mixing of the mixer fluid and the tank fluid in the conduit.

[0025] Optionally, the duct includes a diffuser section between the opening and the duct outlet, wherein the internal cross-sectional area of ​​the diffuser section increases with increasing distance from the opening toward the duct outlet. This can reduce the velocity and / or increase the pressure of the outlet fluid supplied to the duct outlet. This in turn can reduce the operating noise of the ventilation duct.

[0026] Optionally, the ventilation system includes a controller configured to: move the tank fuel through the opening toward the conduit outlet; and simultaneously enable operation of the fluid mover to move the mixer fluid through the conduit and mix with the tank fuel upstream of the conduit outlet.

[0027] The fuel tank venting system may include a supply valve that is fluidly connected or connectable between the fuel tank and the opening. The supply valve may be operated, such as by the controller, to connect the fuel tank fluid to the conduit via the opening. Optionally, the controller is configured to open the fuel supply valve in order to move the tank fuel through the opening toward the conduit outlet.

[0028] Optionally, the fuel tank is an aircraft fuel tank and the vent tube is a ground-based vent tube that can be connected to the aircraft fuel tank via the opening during refueling of the aircraft fuel tank. Providing such a vent tube separate from the aircraft can allow tank fluid, such as hydrogen fuel for the aircraft, to be discharged to a location away from the aircraft and / or away from personnel working on the aircraft. This can improve the safety of the vent tube.

[0029] Optionally, the vent duct is removable. For example, the vent duct may include at least one vehicle component, such as a wheel, roller and / or track. Providing a removable vent duct may provide a universal vent duct that can be moved to the location of an aircraft. Optionally, the vent duct is part of a fuel filling system, such as a ground-based fuel filling system, such as a removable fuel filling system. Providing such a removable vent duct and / or fuel filling system may provide an independent unit that may be used to refuel the fuel tanks of a variety of different aircraft and / or may provide versatility in the location of such an aircraft.

[0030] A second aspect of the present invention provides a fuel filling system comprising: a fuel source connectable to a fuel tank to supply fuel to the fuel tank; and the ventilation system of the first aspect of the present invention.

[0031] Optionally, the fuel source includes a fuel outlet line that can be connected to the fuel tank to supply fuel to the fuel tank while the fuel tank is connected to the ventilation system. In this way, gaseous fuel, such as gaseous hydrogen fuel, in the fuel tank can be discharged from the fuel tank, while liquid fuel, such as liquid hydrogen fuel, is supplied to the fuel tank via the fuel outlet line. Thus, the fuel filling system can provide a self-contained unit for filling the fuel tank while safely removing unused or remaining fuel from the fuel tank.

[0032] A third aspect of the invention provides a method of venting tank fluid from a fuel tank to atmosphere outside the fuel tank using a vent system. The vent system comprises: a conduit comprising a conduit inlet and a conduit outlet, the conduit outlet opening to atmosphere outside the conduit; and an opening opening into the conduit between the conduit inlet and the conduit outlet, the opening being fluidly connected or connectable to the fuel tank. The method comprises: moving the tank fluid from the fuel tank through the opening toward the conduit outlet; and simultaneously, flowing a mixer fluid that may be received in the conduit inlet through the conduit toward the conduit outlet, thereby mixing the mixer fluid with the tank fluid in the conduit upstream of the conduit outlet.

[0033] The ventilation system may be the ventilation system of the first aspect of the invention. It will be appreciated that the method may include and / or benefit from any of the optional features and / or advantages of the ventilation system of the first aspect of the invention and / or the fuel filling system of the second aspect of the invention. For example, the ventilation system may include the (or each) fluid propeller, and causing a mixer fluid that may be received in the conduit inlet to flow through the conduit toward the conduit outlet may include operating the fluid propeller (or one or more fluid propellers in the fluid propellers). In addition, where the ventilation system includes a supply valve, causing the tank fluid to move from the fuel tank through the opening toward the conduit outlet may include opening the supply valve.

[0034] Optionally, the method includes moving the mixer fluid through the conduit at a volumetric flow rate that is at least 25 times the volumetric flow rate of the tank fluid through the opening.

[0035] Optionally, the method includes moving the mixer fluid through the conduit at a volumetric flow rate equal to or greater than 50 times, such as equal to or greater than 75 times, such as equal to or greater than 100 times, such as equal to or greater than 200 times, the volumetric flow rate of the tank fluid through the opening. The higher volumetric flow rate of the mixer fluid through the conduit relative to the volumetric flow rate of the tank fluid through the opening can provide greater mixing and / or dilution of the tank fluid components in the conduit upstream of the conduit outlet. As described above, this can reduce the flammability of the outlet fluid when the components are flammable components.

[0036] Optionally, the method includes passing the mixer fluid through the conduit at a certain volume flow rate, the volume flow rate causing the outlet fluid discharged from the outlet of the conduit to have a concentration of the tank fluid component of up to 4 volume%, up to 2 volume%, up to 1 volume%, such as up to 0.5 volume%, such as up to 0.1 volume%, or less than 0.05 volume%. This can cause the concentration of the component in the outlet fluid to be less than the LFL of the component, where the component is a combustible component. For example, when the component is hydrogen fuel, the volume flow rate of the mixer fluid can cause the outlet fluid discharged from the outlet of the conduit to have a tank fluid component concentration of at least less than 4 volume%, which is the approximate LFL of hydrogen. Providing a volume flow rate of the mixer fluid that causes the concentration of the component in the outlet fluid to be less than the LFL of the component can improve the safety of the ventilation system.

[0037] Optionally, the method comprises operating the or each fluid mover at a speed to provide the corresponding mass flow rate.

[0038] Optionally, the method is a computer-implemented method, such as a method that may be implemented by a controller of the ventilation system of the first aspect of the invention if provided.

[0039] A fourth aspect of the present invention provides a non-transitory computer-readable storage medium storing instructions which, when executed by a processor, cause the processor to perform the method of the third aspect of the present invention.

[0040] Optionally, the ventilation system of the first aspect of the present invention and / or the fuel filling system of the second aspect of the present invention comprises a non-transitory computer readable storage medium. Optionally, in the case where a controller is provided, the controller comprises a processor configured to execute instructions stored on the computer readable storage medium.

[0041] It will be appreciated that the computer-readable storage medium of the fourth aspect of the invention may include and / or benefit from any of the optional features and / or advantages of any one or more of the first to third aspects of the invention, respectively. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

[0043] Figure 1 A schematic diagram of an example aircraft and fueling system is shown;

[0044] Figure 2 Shown for Figure 1 A schematic diagram of an example fuel filling system for refueling a fuel tank of an aircraft; and

[0045] Figure 3 Shows the Figure 1 An example method for draining a fuel tank of an aircraft. DETAILED DESCRIPTION

[0046] Figure 1 An example aircraft 1 is shown. The aircraft is shown on the ground and includes a fuel tank 3 for storing fuel and supplying fuel to the engine 8 of the aircraft 1. Here, the fuel is hydrogen fuel, which is stored exclusively in the aircraft fuel tank 3 as cryogenic liquid hydrogen. However, it will be understood that the disclosure herein is similarly applicable to fuel systems configured to store any other suitable type of fuel, such as conventional aviation fuel such as kerosene. In addition, although the fuel tank 3 is shown as being near the rear of the aircraft 1, near the tail 6 of the aircraft, in other examples, the fuel tank 3 may be located in any other suitable location, such as centrally located in the aircraft 1 and / or partially located within the wing 7 and / or tail 6 of the aircraft 1.

[0047] Figure 1 Also shown is a fuel filling system 5, which includes a fuel source 4 for supplying fuel to the fuel tank 3. The fuel filling system 5 also includes a ventilation system 2, which is used to discharge gaseous hydrogen in the fuel tank 3 to the atmosphere 6 outside the fuel tank 3 via the outlet 21b of the ventilation system 2 during the fuel filling of the fuel tank 3 through the fuel filling system 5. The fuel filling system 5 is a ground-based mobile fuel filling system that can be moved to the aircraft 1 to allow the fuel filling operation of the fuel tank 3. Figure 1 , the ventilation system 2 is configured such that the outlet 21 b of the ventilation system 2 is positioned above the highest point of the aircraft 1 when the aircraft 1 is on the ground adjacent to the ventilation system 2. This allows the hydrogen fuel from the fuel tank 3 to be discharged both away from ground personnel performing fueling operations (and / or other operations) and away from components of the aircraft 1, thereby improving the safety associated with the use of the ventilation system 2.

[0048] Figure 2 A more detailed schematic diagram of a fuel filling system 5 is shown. The fuel supply arrangement 4 comprises a supply tank 40 which, in use and as shown, is fluidly connected to the fuel tank 3 via a fuel supply valve 41. The supply tank 40 contains pressurized liquid hydrogen fuel. When the fuel supply valve 41 is opened, the pressure in the supply tank 40 causes the liquid hydrogen fuel to move from the supply tank 40 to the fuel tank 3. This causes the pressure in the fuel tank 3 to increase. The pressure in the fuel tank 3 is relieved by venting the gaseous hydrogen fuel from the ullage space 31 of the fuel tank 3 through the vent system 2 to the atmosphere 6 outside the fuel tank 3. This allows the fuel level 32 in the fuel tank 3 to increase, as caused by Figure 2 As indicated by the arrow marked 35.

[0049] The ventilation system 2 includes a ventilation duct 20, which includes a duct 21 and a manifold 22. The manifold 22 includes six openings (for simplicity, collectively referred to by the reference numeral "23") that pass through a side wall 27 of the manifold 22 and enter the duct 21. The openings 23 are located at Figure 2 2 is shown as a breach in the side wall 27 of the manifold 22. The manifold 22 itself is defined by the end of a conduit 51 that fluidly connects the opening 23 to the ullage space 31 in the fuel tank 3 via a tank gas valve 52 of the vent system 5. The tank gas valve 52 is opened during refueling of the fuel tank 3 (i.e., when the fuel supply valve 41 is open) to allow gas to pass from the ullage space 31 to the conduit 21 via the opening 23.

[0050] The duct 21 includes a duct inlet 21a and a duct outlet 21b, which is the outlet 21b of the ventilation system 2 described above. The manifold 22 is positioned so that each opening 23 leads to the duct 21 between the duct inlet 21a and the duct outlet 21b. Here, the openings 23 are spaced apart in an array extending around the circumference of the side wall 27 of the manifold 22, but it will be understood that in other examples, the openings 23 may be provided in any other suitable arrangement.

[0051] The ventilation duct 2 further includes a fan 25 operable to convey air outside the ventilation duct 2 from the duct inlet 21a through the duct 21 to the duct outlet 21b. Figure 2 Only one fan 25 is shown in the figure, but three such fans are provided in this example (for the sake of simplicity, they are referred to by the common reference numeral "25"). However, it will be understood that in other examples, any other suitable number of fans 25 may be provided, such as only one fan, two fans, or more than three fans.

[0052] During refueling of the fuel tank 3, gaseous hydrogen flowing into the conduit 21 through the opening 23 is entrained and mixed in the air moving through the conduit 21 caused by the fan 25. This mixing occurs in the region 26 around the opening 23. When the gaseous hydrogen fuel enters the conduit 21 and mixes with the air near the opening 23, the concentration of hydrogen fuel in the mixture of gaseous hydrogen and air in the region 26 is initially high. This may cause the mixture near the manifold 22 and / or the opening 23 to burn. Therefore, the ventilation tube 2 also includes a layer of thermal insulation material 24, which is located on the inner surface 24a of the conduit 1 and extends circumferentially around the inner surface 24a of the conduit 1 to define a radially enclosed region 26 of the inner wall of the conduit and a portion of the manifold 22 within the region 27. The thermal insulation material 24 extends axially on both sides of the manifold 22 in a direction along the axis 21c of the conduit 21. Thermal insulation material 24 thereby allows the flame to remain near manifold 22 , and in particular in region 26 , while increasing the life of inner surface 24a of conduit 21 and limiting the temperature rise on the exterior of conduit 21 .

[0053] The fans 25 can be operated at a flow rate sufficient to ensure that the hydrogen fuel and air in the duct are mixed so that the mixture of hydrogen and air downstream of the region 26 and upstream of the duct outlet 21b drops below its lower flammable limit (LFL). In particular, each fan 25 is sized to provide a volume flow rate of air through the duct 21 that is equal to or greater than 50 times, such as equal to or greater than 75 times, such as equal to or greater than 100 times, such as equal to or greater than 200 times the volume flow rate of hydrogen entering the duct 21 through the common opening 23. This can make the concentration of hydrogen in the mixture of hydrogen and air at the duct outlet 21b up to 4% by volume, such as up to 2% by volume, such as up to 1% by volume, such as up to 0.5% by volume, such as up to 0.1% by volume, or less than 0.05% by volume. This ensures that there is no flame at or downstream of the duct outlet 21b, thereby improving the safety of the ventilation duct 2. A flame in a cross flow has a lower thermal emissivity than a flame in a static atmosphere. It will therefore be appreciated that increasing the volumetric flow rate of cross-flow air in duct 21 provided by fan 25 relative to hydrogen flowing into duct 21 may reduce the heat radiated by flames present in region 26 , which may improve the safety of ventilation system 2 .

[0054] A blade system 29 is provided upstream of the manifold 22 and downstream of the fan 25 to passively increase the amount of turbulence imparted to the air passing through the duct 21. The blade system 29 includes blades that are oriented to impart a swirl component to the air flow through the duct 21 upstream of the opening 23 in the manifold 22. This turbulent and / or swirl flow can increase the mixing rate of the hydrogen fuel with the air in the region 26. It will be appreciated that the mixing of the hydrogen fuel and air in the region 26 ultimately reduces the amount of hydrogen fuel in the mixture to below the LFL of the mixture as described above, thereby preventing further combustion of the mixture in the duct 21. By increasing the amount of turbulence in the airflow, the blade system 29 increases the mixing rate in the region 26, thereby reducing the concentration of hydrogen in the mixture to below the LFL of the mixture more quickly. It will be appreciated that for ease of understanding, Figure 2 The blade system 29 shown in the figure is schematic and does not represent the actual structure of the blade system 29 and / or the blades of the blade system. It will be understood that the blade system 29 can take any suitable form. It will also be understood that in other examples, the blade system 29 may not be provided, and turbulence may be imparted to the airflow in any other suitable manner.

[0055] The ventilation duct 2 also includes a diffuser 28 located downstream of the manifold 22 and upstream of the duct outlet 21b. The diffuser 28 includes a portion of the duct 21 that increases in cross-sectional area in the direction toward the duct outlet 21b. In this way, when in use, the diffuser 28 increases the pressure of the air transmitted toward the outlet 21b and reduces the speed of the air transmitted toward the outlet 21b, which in turn reduces the noise emitted by the ventilation system 2. In particular, the diffuser 28 is sized to be related to the flow rate provided by the fan 25 to reduce the speed of the mixture of hydrogen fuel and air transmitted from the duct outlet 21b to the atmosphere 6 to less than 10m / s, such as less than 7m / s, such as less than 5m / s. By reducing the speed and increasing the pressure in this way, the diffuser can also reduce the power required to operate the fan 25.

[0056] The ventilation duct 2 also includes a pressure sensor 71 configured and arranged to sense the pressure at the duct inlet 21a upstream of the fan 25. The pressure at the duct inlet 21a indicates the operation of the fan 25: when the fan 25 is operating, the pressure at the duct inlet 21a decreases. If one or more of the fans 25 stops, or the performance of one or more of the fans 25 decreases, the pressure at the duct inlet 21a will increase. In this way, the pressure sensor 71 allows the performance of one or more of the fans 25 to be determined.

[0057] The ventilation system 2 also includes an inert gas tank 60, which is fluidly connected to the conduit 21 upstream of the opening 23 via an inert gas valve 61. The inert gas tank 60 is a pressure vessel configured to store pressurized nitrogen. In the event of a failure of the ventilation system 2 that causes the concentration of hydrogen in the conduit 21 downstream of the region 26 to increase to a risk of being above the LFL of a mixture of hydrogen and air, the inert gas valve 61 can be opened to allow nitrogen to flush the conduit 21. Such a failure can, for example, include a failure of one or more of the fans 25 that reduces the performance of one or more of the fans 25, or a failure of the tank gas valve 52 that keeps the tank gas valve 52 open. Therefore, the inert gas tank 60 can improve the safety of the ventilation system 2 by providing an alternative fluid source that can be mixed with hydrogen from the tank in the conduit 21.

[0058] like Figure 2 As shown in FIG. 1 , the ventilation system 5 includes a controller 70 configured to execute Figure 3 The computer implemented method 400 is schematically shown in FIG. The controller is communicatively coupled to the fuel supply valve 41 , the tank gas valve 52 , the inert gas valve 61 , the fan 25 , and the pressure sensor 71 .

[0059] Method 400 performed by controller 70 includes supplying 410 liquid hydrogen (LH2) fuel from fuel source 4 to fuel tank 3 by opening fuel supply valve 41. Method 400 also includes moving 420 gaseous hydrogen (GH2) fuel from fuel tank 3 to conduit 21 by opening tank gas valve 52.

[0060] like Figure 3 As shown in , the method 400 performed by the controller 70 also includes receiving 430 information indicating the flow rate of air in the duct 21 from the pressure sensor 71. Here, the information is a pressure level at the duct inlet 21a as described above indicating the performance of the fan 25 and the flow rate of air in the duct 21. The method 400 then includes the controller 70 comparing 440 the information with reference information. In particular, the method 400 includes the controller 70 comparing the pressure received from the pressure sensor 71 with the reference pressure. If the comparison indicates that the flow rate is high enough to allow sufficient mixing of the gas and air flow in the duct as discussed above, the method 400 includes the controller 70 causing 450 GH2 fuel to be supplied from the fuel tank to the duct 21 by causing the tank gas valve 52 to open. In this case, the flow rate is considered to be high enough when the pressure at the duct inlet 21a is lower than the reference pressure.

[0061] Then, receiving 430 and comparing 440 information are repeated in a loop to allow the controller 70 to continuously monitor whether the mass flow of air through the conduit 21 is sufficiently high. If at any time the comparison indicates that the mass flow of air through the conduit 21 is insufficient (in this case, when the pressure at the conduit inlet 21a is at or above the reference pressure), the method 400 includes the controller 70 preventing 460GH2 from being supplied to the conduit 21 by causing the tank gas valve 52 to close. Here, the method 400 also includes: in the event that the mass flow of air through the conduit 21 decreases, causing 470 inert gas to be supplied to the conduit 21 from the inert gas tank 60 by causing the inert gas valve 61 to open. This allows any hydrogen still present in the conduit after closing the tank gas valve 52 to be flushed from the conduit using the inert gas. The causing 470 inert gas to be supplied to the conduit 21 can be performed before, after, or simultaneously with preventing 460GH2 from being supplied to the conduit 21.

[0062] Then, receiving 430 and comparing 440 information are repeated again after preventing 460 GH2 from being supplied to the duct 21 and / or after enabling 470 inert gas to be supplied to the duct 21. In this way, if the mass flow rate of air through the duct 21 increases to a level deemed sufficient for proper mixing of GH2 with the air in the duct, GH2 can be supplied to the ventilation duct again.

[0063] The controller 70 includes a processor configured to execute instructions to cause the controller 70 to perform the method 400. The controller 70 includes a non-transitory computer-readable storage medium storing instructions that, when executed by the processor of the controller 70, cause the processor to perform the method 400 described above.

[0064] In some examples, in addition to or in lieu of opening 23, manifold 23 may include any other suitable opening to conduit 21. For example, manifold 23 may include any other number of openings, such as only one opening, up to six openings, or more than six openings. In other examples where manifold 23 includes only a single other opening, the single or other opening may be formed by a nozzle (not shown) that opens to conduit 21. Alternatively, manifold 22 may include opening 23 through a side wall 27 of manifold 22 and a nozzle defined at an end of manifold 22, such as Figure 2 At the end of the manifold 22 facing the conduit outlet 21b.

[0065] It will be appreciated that in other examples, the method 400 may alternatively be performed manually, such as by an operator manually causing operation of the fan 25 and / or the tank gas valve 52. Furthermore, while the method 400 includes receiving 430 a pressure signal from the pressure sensor 71 at the duct inlet 21a to infer the performance of the fan 25 and / or the flow through the duct 21, in other examples, the performance of the fan 25 and / or the flow through the duct 21 may be determined in any other suitable manner. For example, the controller 70 may be configured to receive information representing the speed of the corresponding one or more fans 25 from one or more of the fans 25, and compare the fan speed to a reference fan speed. In this case, a decrease in the speed of the corresponding one or more fans 25 may indicate a decrease in the flow in the duct 21, which may cause the tank gas valve 52 to close. Alternatively or additionally, the controller 70 may receive information representing the pressure and / or flow downstream of one or more fans 25 in the duct 21, and compare the pressure and / or flow to a corresponding reference pressure and / or reference flow. In other examples, the controller 70 may receive information representing an amount of vibration of one or more of the fans 25 and use the information to infer the speed of the corresponding one or more fans and / or the mass flow rate provided by the corresponding one or more fans 25. In some examples, the ventilation system 2 includes a composition sensor (not shown) that obtains information representing the composition of the mixture of air and hydrogen in the conduit 21. The composition of the mixture can be used to determine whether to open and / or close the tank gas valve 52 and / or the inert gas supply valve 61. Other ways of determining a suitable flow through the conduit 21 will be apparent to those skilled in the art. For example, conditions in the conduit, such as conditions upstream of the region 26, downstream of the region 26, or within the region 26, can be inferred using any suitable parameter of the flow of hydrogen and / or air through the conduit 21, such as pressure, temperature, composition, flow, or vibration.

[0066] It should be noted that, unless explicitly stated otherwise, the term “or” used in this document should be interpreted as meaning “and / or”.

Claims

1. A vent system comprising a vent tube for discharging tank fluid from a fuel tank external to the vent tube during refueling of the fuel tank, the vent tube comprising: a conduit, the conduit comprising a conduit inlet and a conduit outlet, the conduit outlet leading to atmosphere outside the conduit; an opening leading to the conduit between the conduit inlet and the conduit outlet, the opening being fluidly connected or connectable to the fuel tank such that, in use, tank fluid flows from the fuel tank through the opening to the conduit outlet; as well as A fluid mover is operable to cause a mixer fluid receivable in the conduit inlet to flow through the conduit toward the conduit outlet, thereby mixing the mixer fluid with the tank fluid in the conduit upstream of the conduit outlet.

2. The ventilation system according to claim 1, wherein: The fluid mover is a first fluid mover and the ventilation system includes one or more additional fluid movers, and the additional fluid mover or each additional fluid mover is capable of being operated to cause the mixer fluid that can be received in the inlet of the conduit to flow through the conduit toward the conduit outlet, thereby mixing the mixer fluid with the tank fluid in the conduit upstream of the conduit outlet.

3. A ventilation system according to any one of claims 1 or 2, wherein: The vent tube includes a geometry configured to impart turbulence into the mixer fluid upstream of the opening.

4. The ventilation system according to any one of claims 1 to 3, wherein: At least a portion of an inner wall of the conduit downstream of the opening comprises a thermally insulating material.

5. The ventilation system according to any one of claims 1 to 4, wherein: At least a portion of the opening is spaced from each portion of the inner wall of the conduit by an amount greater than 20% of a minimum distance between opposing sides of the conduit.

6. The ventilation system according to any one of claims 1 to 5, wherein: the opening is a first opening and the vent comprises one or more further openings leading to the duct between the duct inlet and the duct outlet, Wherein the or each further opening is fluidly connected or connectable to the fuel tank such that, in use, tank fluid flows from the fuel tank through the respective further opening to the conduit outlet.

7. The ventilation system according to any one of claims 1 to 6, wherein: The or each opening is at least partly defined by an aperture in a side wall of a conduit in the catheter.

8. The ventilation system according to any one of claims 1 to 7, wherein: The duct includes a diffuser section between the opening and the duct outlet, wherein an internal cross-sectional area of ​​the diffuser section increases with increasing distance from the opening toward the duct outlet.

9. The ventilation system according to any one of claims 1 to 8, comprising a controller configured to: moving the tank fuel through the opening toward the conduit outlet; and The fluid mover is simultaneously operated to move the mixer fluid through the conduit and mix with the tank fuel upstream of the conduit outlet.

10. The ventilation system according to any one of claims 1 to 9, wherein: The fuel tank is an aircraft fuel tank and the vent tube is a ground-based vent tube connectable to the aircraft fuel tank via the opening in a fueling bay of the aircraft fuel tank.

11. A fuel filling system, comprising: a fuel source connectable to the fuel tank to supply fuel to the fuel tank; as well as A ventilation system according to any one of claims 1 to 10.

12. A method of draining a tank fluid, the method draining the tank fluid from a fuel tank to the atmosphere external to the fuel tank using a vent system, the vent system comprising: a conduit, the conduit comprising a conduit inlet and a conduit outlet, the conduit outlet leading to atmosphere outside the conduit; as well as an opening leading to the conduit between the conduit inlet and the conduit outlet, the opening being fluidly connected or connectable to the fuel tank; The method comprises: moving the tank fluid from the fuel tank through the opening toward the conduit outlet; and Simultaneously, a mixer fluid receivable in the conduit inlet is caused to flow through the conduit toward the conduit outlet, thereby mixing the mixer fluid with the tank fluid in the conduit upstream of the conduit outlet.

13. The method of claim 12, comprising moving the mixer fluid through the conduit at a mass flow rate that is at least 25 times the mass flow rate of the tank fluid through the opening.

14. A non-transitory computer-readable storage medium storing instructions which, when executed by a processor, cause the processor to perform the method according to claim 12 or claim 13.

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