Aircraft fuel system, aircraft, and method of operating an aircraft

Abstract

The present invention relates to an aircraft fuel system, an aircraft, and a method of operating an aircraft. The aircraft fuel system includes a fuel line configured to fluidly connect a fuel tank to a fuel consuming component. The fuel line includes a fuel conduit and a structure fluidly connected to the fuel conduit to fluidly connect the fuel tank to the fuel consuming component. The structure includes an inlet and an outlet for delivering aircraft fuel from the fuel tank to the fuel consuming component through an internal volume of the structure. A cross-sectional area of the internal volume of the structure is greater than a cross-sectional area of an interior of the fuel conduit, and the structure includes a fluid refill port fluidly connecting the interior of the structure to an exterior of the structure and through which fluid can be provided to the structure. The aircraft includes the aircraft fuel system.

Description

Technical Field

[0001] This invention relates to aircraft fuel systems. Background Technology

[0002] Aircraft include fuel systems for storing and utilizing aircraft fuel. However, using aircraft fuel produces undesirable emissions into the atmosphere. It is desirable to improve aircraft fuel systems to contribute to the reduction of these undesirable emissions. Summary of the Invention

[0003] A first aspect of the invention provides an aircraft fuel system. The aircraft fuel system includes a fuel line configured to fluidly connect a fuel tank to a fuel consumption component. The fuel line includes a fuel conduit for fluidly connecting the fuel tank to the fuel consumption component, and a structure fluidly connected to the fuel conduit. The structure includes an inlet and an outlet for conveying aircraft fuel from the fuel tank to the fuel consumption component through an internal volume of the structure, the cross-sectional area of ​​the internal volume of the structure being larger than the cross-sectional area of ​​the internal volume of the fuel conduit. The structure includes a fluid refill port fluidly connecting the interior of the structure to the exterior of the structure, and aircraft fuel can be supplied to the structure through the fluid refill port.

[0004] According to the first aspect, the aircraft fuel system can be operated to store aircraft fuel additives in its structure while storing aircraft fuel in its fuel tank. The aircraft fuel system can then be operated to supply aircraft fuel, including the aircraft fuel additives, to a fuel-consuming component at a first time. The fuel-consuming component consumes the aircraft fuel mixed with the aircraft fuel additives at this first time, and in doing so, for example, compared to consuming aircraft fuel without such fuel additives, can produce fewer undesirable emissions, such as soot, nitrogen oxides, sulfur oxides, or other non-CO2 emissions. Through the operation of the fuel-consuming component, the contents of the fuel line structure, such as the aircraft fuel mixed with the aircraft fuel additives, are depleted. At a later, second time, the aircraft fuel from the fuel tank can then be used by the fuel-consuming component.

[0005] Similarly, the aircraft fuel system according to the first aspect can be operated to, for example, store another type of aircraft fuel, such as synthetic or sustainable aviation fuel (SAF), within the structure, while the fuel tank stores conventional aircraft fuel. More generally, the fuel tank can store the first type of aircraft fuel, and the structure can store a second, different type of aircraft fuel. SAF can be supplied to the fuel consumption component at a first time, and conventional aircraft fuel from the fuel tank can be supplied to the fuel consumption component at a second, later time. SAF can produce reduced particulate emissions when used, which is desirable for air quality.

[0006] In these ways, aircraft fuel systems promote multi-stage fuel consumption. Fuel lines can be structured to maintain sufficient quantities of fuel or fuel additives for operations within an associated operational timeframe. For example, the associated operational timeframe might encompass the expected duration the aircraft will operate on the ground. Therefore, while the aircraft is operating on the ground—such as during loading, unloading, taxiing, or maintenance—fuel consumption components are supplied with and consume a blend of aircraft fuel and fuel additives. Consequently, the aircraft can generate fewer emissions during this operational timeframe. Once the aircraft is in flight, fuel consumption components can primarily consume fuel already stored in the fuel tanks, which may not necessarily include fuel additives. Ground operations of the aircraft may be subject to emission restrictions to protect local air quality, while air operations may not be subject to such emission restrictions.

[0007] The structure is integrated into the fuel lines that connect the fuel tank to the fuel consumption components. In some examples, the structure can be retrofitted into existing fuel systems, thereby facilitating multi-stage fuel consumption in existing aircraft. This modification may require only limited architectural changes, as the fuel systems described herein can take a relatively simple form and operate passively, as will be described later.

[0008] The structure has an internal volume with a cross-sectional area larger than that of the fuel conduit, thus allowing for a larger volume per length compared to the fuel conduit. This allows for enhanced fuel storage capacity for a given footprint of the fuel line compared to the fuel conduit. Furthermore, in the context of modified applications, for example, the length of the fuel conduit replaced by the structure according to this disclosure means that the fuel line can operate to store an increased total volume of fluid within the fuel line. The cross-sectional area can be measured in a plane perpendicular to the direction of fluid flow through the main body of the fuel line. In some examples, the total internal volume of the structure is greater than the total volume of the fuel conduit in the fuel line.

[0009] As used herein, "fuel tank" refers to a storage volume for storing fuel in an aircraft. In some examples, a fuel tank may be an internal fuel storage tank, such as an internal fuel tank located within the fuselage or wing of an aircraft. As used herein, "fuel conduit" refers to an element, such as a fuel pipeline, operable to deliver fuel from a fuel tank to a fuel-consuming component. As used herein, "fuel-consuming component" refers to a component that utilizes fuel, for example, by combustion, to generate mechanical or electrical power. It will be understood that "fuel-consuming component" refers to a component configured to consume fuel, and that a "fuel-consuming component" does not require the component to be in a fuel-consuming state. A fuel-consuming component may be an auxiliary power unit, for example, an auxiliary power unit operable to generate energy for operations other than propulsion. A fuel-consuming component may be a jet engine of an aircraft. It will be understood that an aircraft fuel system may include fuel lines configured to fluidly connect multiple fuel tanks to multiple fuel-consuming components. A “fluid refueling port” can fluidly connect a structure to a fluid source, such as a blend of aircraft fuel and aircraft fuel additives, undiluted aircraft fuel additives, or another aircraft fuel, such as SAF, located outside the aircraft, such as an aircraft refueling device independent of the aircraft.

[0010] As used herein, “aircraft fuel” refers to conventional aviation fuel such as Jet A or Jet A1 fuel, which is typically hydrocarbon-based and, in particular, kerosene-based. As used herein, “aircraft fuel additive” refers to a substance added to aircraft fuel for purposes such as reducing unwanted emissions. Aircraft fuel additives described herein may also include, for example, icing inhibitors, corrosion inhibitors, metal deactivators, static dissipation additives, and biocides. Structures capable of storing aircraft fuel additives can store them in concentrated, undiluted, or unblended forms. Structures can alternatively store aircraft fuel additives in blended forms, wherein the aircraft fuel additive is blended with the aircraft fuel. For brevity, the resulting mixture of aircraft fuel additive and aircraft fuel may be simply referred to herein as an “additive-fuel blend.” Furthermore, unless otherwise stated, references to “fuel additive” should be understood to mean either unblended or blended forms. For example, a structure storing fuel additives could mean that an additive-fuel blend is stored, or that undiluted fuel additive is stored. “SAF” refers to synthetic or sustainable aviation fuel. SAF is an alternative form of aircraft fuel. SAF can be, for example, non-petroleum-based and designed to replace conventional aircraft fuel. For example, these can be derived from biomass.

[0011] The structure of the fuel pipeline described herein can be used to store something different from a fuel tank. Therefore, where a structure or fuel system is described as storing, for example, aircraft fuel additives or aircraft fuel additive blends, or supplying, for example, aircraft fuel additives or aircraft fuel additive blends to fuel-consuming components, it will be understood that, unless explicitly stated otherwise, this description can also be applied to storing and / or releasing another type of aircraft fuel, such as SAF. For example, this other type of aircraft fuel does not necessarily include aircraft fuel additives.

[0012] Aircraft fuel typically flows from the fuel tank to the fuel consumption component. As used herein, the "main fuel flow direction" refers to the general or net direction of fuel movement, which can generally be considered as the direction along the fuel duct and from the inlet to the outlet of the fuel structure. It will be understood that the existence of regions where the fluid flows locally in a direction different from the main fuel flow direction, for example due to eddies in turbulent regions, does not negate the existence of the overall main fuel flow direction. The main fuel flow direction can be a path conformal to and / or to the structure of the fuel duct, as the main fuel flow direction can differ in different corresponding regions of the fuel line, although it simultaneously follows the overall path of fuel from the fuel tank to the fuel consumption component.

[0013] Optionally, the cross-sectional area of ​​the structure is greater than twice the cross-sectional area of ​​the fuel conduit; alternatively, the cross-sectional area is greater than three times the cross-sectional area of ​​the fuel conduit. In some examples, the cross-sectional area is greater than five times the cross-sectional area of ​​the fuel conduit. In some examples, the volume per length of the structure (e.g., which may also be considered as the average cross-sectional area) is greater than twice, for example, greater than three times, or greater than five times the volume per length of the fuel conduit. In some examples, the total volume of the structure is greater than twice, for example, greater than three times, or greater than five times the volume of the fuel conduit having an equivalent occupied space. In some examples, the total volume of the structure is greater than twice, for example, greater than three times, or greater than five times the volume of the fuel conduit having an equivalent occupied space.

[0014] Optionally, the structure has a volume exceeding 100 liters. In some examples, the volume exceeds 300 liters. In some examples, the volume exceeds 500 liters. The structure can be sized to store a sufficient amount of aircraft fuel additive to facilitate the operation of fuel-consuming components within a desired operating timeframe, such as when operating on the ground. In other examples, the structure has a volume less than 100 liters, such as 10 liters or less. This can reduce the space occupied by the structure. In such examples, the structure can store undiluted aircraft fuel additive.

[0015] Optionally, the structure includes a gas relief valve operable to release gas from the internal volume of the structure to the outside of the structure, optionally located in the top portion of the structure. This allows air or other gases to escape from the fuel line and reduces fuel venting before the fuel reaches the fuel consumption component. Fuel venting can be detrimental to the function of the fuel consumption component. In some examples, the structure includes a reservoir portion below the inlet to facilitate air-fuel separation, and the gas relief valve is located above the reservoir portion. The reservoir portion may be a second region as described later.

[0016] Optionally, the structure also includes a liquid discharge port through which liquid within the structure can be released to the outside of the structure. This can, for example, facilitate the discharge of liquid from a structure independent of the fuel tank. In some examples, the liquid discharge port is integrated with the fluid refill port as a bidirectional liquid port. This can reduce the space occupied by joints in the structure.

[0017] Optionally, the internal volume of the structure has a cross-sectional area that gradually varies along the main fuel flow direction through the structure. This gradual change in cross-sectional area can improve the fluid flow characteristics through the structure, for example, by reducing turbulence that may occur at abrupt changes in the cross-sectional profile. In some examples, the cross-sectional area increases with distance from the inlet and outlet, such that the cross-sectional area is maximized at an intermediate location between the inlet and outlet. In some examples, the change in cross-sectional area does not exceed about one-tenth of a unit of length; for example, the walls of the internal volume have an inclination angle of no more than 6 degrees relative to the main fuel flow direction through the structure. This can reduce the amount of air released from the fuel, which could accumulate as bubbles and potentially disrupt the fuel supply to the fuel-consuming components.

[0018] Optionally, the structure includes a barrier element located within an internal volume of the structure, forming at least a portion of the boundary between a first region and a second region of the internal volume, wherein, in use, the majority of the main fuel flow direction from inlet to outlet passes through the first region. Providing a barrier element can help demarcate the fuel storage area of ​​the internal volume, performed by the second region, from the fuel flow area of ​​the internal volume, performed by the first region. The barrier element can serve as a fuel flow guide to facilitate the main fuel flow direction directly from inlet to outlet, thereby, for example, maintaining the flow rate of fuel through the structure. In some examples, the barrier element can form a total boundary between the first and second regions of the internal volume, thus prohibiting fluid movement between the second and first regions. The barrier element can optionally be reconfigured to allow fluid movement from the first region to the second region. In other examples, the barrier element can be used to provide a substantial barrier between the first and second regions (wherein the barrier is positioned over a majority of the area between the first and second regions), but the first and second regions remain fluidly connected to each other.

[0019] Optionally, the barrier element is perforated, allowing fluid to move from the second region to the first region. The barrier element in its perforated state may comprise an array of through-holes extending through the barrier element. The array of holes may be a regular arrangement of the through-holes, such as a hexagonal grid. The holes may be sized such that the through-holes constitute a small portion of the surface area of ​​the barrier element, and the majority of the surface area of ​​the barrier element is a solid surface. In some examples, the barrier element is a perforated conduit extending between an inlet and an outlet. In other words, the barrier element has a cylindrical structure. The barrier structure is a perforated conduit extending between an inlet and an outlet, thereby facilitating the main fuel flow direction from the inlet to the outlet, while allowing fuel additives or another fuel in the second region to flow into the first region, and thereby be conveyed out of the structure and delivered to the fuel consumption component.

[0020] Optionally, the structure includes a guide conduit extending from the second region through the barrier element to the first region, thereby providing a fluid path from the second region to the first region. In use, fuel flow through the structure in the main fuel flow direction can be guided through the guide conduit from the second region to the first region. This can facilitate the passive supply of fuel or additives from the second region to the first region, since, for example, movement from the second region to the first region does not require operation of power components within the structure.

[0021] Optionally, the geometric center of the structure is offset from the axis extending from the inlet to the outlet. In this way, the structure incorporates an asymmetric design, where the inlet and outlet are not collinear with the geometric center of the structure. This allows a significant portion of the structure's internal volume to be offset relative to the flow path between the inlet and outlet. This can facilitate demarcation between the storage area and the flow area throughout the structure. Furthermore, the asymmetric design can facilitate the structure being accommodated by the surrounding structures of the aircraft, as the structure can extend into the area of ​​available volume. The geometric center can be the centroid of the structure's internal volume.

[0022] Alternatively, most of the structure's internal volume is located below the axis. In this way, the fluid stored within the structure is held primarily below the fluid flow path between the inlet and outlet by gravity. In the example where the air valve is located in the top section, the arrangement of the internal volume below the axis can more effectively facilitate the removal of air from the fuel as it enters the structure, for example, where most of the internal volume serves as a reservoir. In the example where a barrier is present, the barrier can be constructed as a "false bottom" that horizontally divides the structure's internal volume, such that most of the structure's internal volume is located below the barrier, and the flow path connecting the inlet to the outlet is located above the barrier.

[0023] Optionally, the axis extending from the inlet to the outlet intersects the first region, and the second region forms most of the volume of the structure. In this way, the barrier element acts as the boundary of the main fuel flow through the structure from the inlet to the outlet, thereby helping to maintain the flow rate through the structure.

[0024] Preferably, the fuel conduit includes a first fuel line and a second fuel line, and the structure fluidly connects the first fuel line to the second fuel line. The series connection of the first fuel line, the structure, and the second fuel line fluidly connects the fuel tank to the fuel-consuming component. In other words, the structure is located at an intermediate position on the fuel line between the fuel tank and the fuel-consuming component. It will be understood that being located at an intermediate position on the fuel line between the fuel tank and the fuel-consuming component implies the existence of a flow path from the fuel tank through the fuel structure to the fuel-consuming component—the structure does not need to be physically located between the fuel tank and the fuel-consuming component (e.g., the layout of the fuel line could allow the structure to be located at another location while the aforementioned flow path still exists). In other examples, the structure engages directly with the fuel tank or the fuel-consuming component, such that the fuel conduit extends only between the fuel-consuming component and the structure or between the fuel tank and the structure, respectively.

[0025] Alternatively, the structure can be considered as an extension of the fuel line operable as a fluid storage structure and positioned along a portion of the length of the fuel line, the extension having a larger cross-sectional area compared to the preceding and / or following conduit of the fuel line. In some examples, the conduit of the fuel line may include a wall defining an orifice having a first cross-sectional area. The extension operable as a fluid storage structure has a wall defining an extended orifice having a second cross-sectional area greater than the first cross-sectional area. This can provide a relatively simple construction for the structure, for example, the structure can be more easily retrofitted into an aircraft due to its similarity in geometry to the existing conduit the structure is replacing.

[0026] A second aspect of the invention provides an aircraft comprising an aircraft fuel system according to the first aspect. The aircraft includes fuel lines, a fuel tank, and fuel consumption components. The aircraft can benefit from multi-stage fuel use as described with respect to the first aspect. For example, when on the ground, the aircraft can use fuel-additive blends or SAFs, for example, to reduce unwanted emissions, wherein the structure acts as a relatively small-scale storage container for fuel additives or SAFs. For example, once airborne, the aircraft can then use the fuel stored in the fuel tank.

[0027] Optionally, the fuel tank stores aircraft fuel, and the fuel pipeline is structured to store aircraft fuel additives or another type of aircraft fuel different from the aircraft fuel stored in the fuel tank. This other fuel can be synthetic or sustainable aviation fuel (SAF). It will be understood that, by contrast, this disclosure also provides an aircraft fuel system that does not contain fuel, but this aircraft fuel system is still advantageous because it provides a fuel system capable of accommodating such fuels.

[0028] Optionally, the fuel line is structured to store a blend of aircraft fuel and aircraft fuel additives. In some examples, the structure stores between 100 liters and 500 liters of the fuel-additive blend.

[0029] Alternatively, the fuel tank and structure can store different substances, such as conventional aircraft fuel in the fuel tank and aircraft fuel-additive blends in the structure.

[0030] Optionally, the fuel-consuming component is the aircraft's auxiliary power unit (APU). The APU provides energy for functions other than propulsion. When the aircraft is operating on the ground, the APU can be the primary energy provider. Therefore, the APU can be operated to consume fuel-additives stored in its structure, thereby reducing unwanted emissions from the APU.

[0031] A third aspect of the invention provides a method of operating an aircraft, the method comprising: supplying aircraft fuel at a fuel tank of the aircraft; supplying (i) another aircraft fuel different from the aircraft fuel supplied at the fuel tank, and / or (ii) an aircraft fuel additive, at a structure of a fuel line fluidly connecting the fuel tank to a fuel consumption component; and consuming the other aircraft fuel and / or the aircraft fuel mixed with the aircraft fuel additive from the structure by a fuel consumer. "Supplying" aircraft fuel at the fuel tank and "supplying" aircraft fuel additive at the structure of the fuel line includes fuels already present, such as a quantity of each fuel already retained from a previous refueling event. According to the discussion of the first and second aspects, this method facilitates multi-stage fuel use for the aircraft. Thus, the contents of the structure including the aircraft fuel additive can be used, for example, to reduce unwanted emissions during ground operations. The aircraft fuel supplied at the fuel tank can be used by the aircraft at a later time. "Different" aircraft fuel from the aircraft fuel supplied at the fuel tank means, for example, that the other aircraft fuel has a different chemical composition than the aircraft fuel, or, for example, that is derived from an alternative source.

[0032] As will be understood from the discussion of the first and second aspects, the method involves providing the fuel tank with contents different from those of the structure, thereby facilitating multi-fuel operation. Different contents mean that the aircraft fuel provided in the fuel tank comprises a mixture of substances different from those stored within the structure as aircraft fuel additives or blends of aircraft fuel additives or alternative fuels, such as SAF. The contents of the structure can be initially used by the fuel consumer when it draws the contents from the fuel line, and the contents of the fuel tank are subsequently used. The use of the contents of the structure may last for a relatively short period compared to the overall operating time of the aircraft, due to, for example, the structure storing, for example, a relatively small volume of fuel additives or alternative fuels. For example, in some embodiments, the contents of the structure may be used on a timescale of minutes, while the contents of the fuel tank are used on a timescale of hours. In examples where, for example, the structure stores a relatively large volume, the contents of the structure can be used over a relatively long period of time.

[0033] Optionally, aircraft fuel mixed with aircraft fuel additives from the structure is consumed at the first moment, and at a second, later time, aircraft fuel from the fuel tank is consumed by the fuel consumer. Optionally, another fuel stored by the structure is consumed at the first moment, and at a second, later time, aircraft fuel from the fuel tank is consumed by the fuel consumer.

[0034] Optionally, providing aircraft fuel at the aircraft's fuel tank includes receiving aircraft fuel through a fuel tank refueling process, during which aircraft fuel is supplied to the fuel tank through a refueling port.

[0035] Optionally, providing (i) another aircraft fuel and / or (ii) aircraft fuel additives at the structure of the fuel line includes receiving the other aircraft fuel and / or aircraft fuel additives separately through a structure refueling process, during which the other aircraft fuel and / or aircraft fuel additives are supplied to the structure through the structure's fluid refueling port. In this way, the structure can be refueled separately from the fuel tank, thereby allowing different fluids to be supplied independently to each of the structure and the fuel tank. For example, the fuel tank can be supplied with aircraft fuel while the structure is being supplied with the additive-fuel blend.

[0036] Alternatively, the fuel consumer is an auxiliary power unit.

[0037] Optionally, at the first moment, the aircraft is on the ground. In some examples, at the second moment, the aircraft is in the air.

[0038] Optional features of any aspect of the invention may be applied equally to any other aspect of the invention where appropriate. In particular, it will be understood that the description of the features of the aircraft fuel system according to the first aspect also applies to aircraft including an aircraft fuel system according to the second aspect. Furthermore, the functions described with respect to the features of the first and second aspects may accordingly form part of the method according to the third aspect. Attached Figure Description

[0039] Embodiments of the invention will now be described by way of example only with reference to the accompanying drawings, in which:

[0040] Figure 1 A schematic diagram of an aircraft fuel system based on an example is shown;

[0041] Figure 2 The structure of an aircraft fuel system, based on an example, is shown;

[0042] Figure 3 The structure of an aircraft fuel system according to another example is shown;

[0043] Figure 4 The structure of an aircraft fuel system according to yet another example is shown;

[0044] Figure 5 The modification installation process for an aircraft fuel system based on an example is shown;

[0045] Figure 6 Additional features of the aircraft fuel system, based on the example, are shown.

[0046] Figure 7 An example of an aircraft equipped with an aircraft fuel system is shown; and

[0047] Figure 8 It is a flowchart depicting the steps performed in the method of operating an aircraft according to the example. Detailed Implementation

[0048] exist Figure 1 The diagram schematically depicts an aircraft fuel system 100 according to this disclosure. The aircraft fuel system 100 is formed by a fuel tank 120, which is connected to a fuel consumption unit 130 via a fuel line 110. The fuel line 110 is formed by a fuel conduit 112 and a storage structure 114, which, for simplicity, will be referred to hereinafter as the "structure". In this example, the fuel consumption unit 130 is an auxiliary power unit (APU) of the aircraft, and the fuel tank 120 is used to store aircraft fuel 202 for use by the APU 130. The fuel line 110 is used to deliver aircraft fuel 202 from the fuel tank 120 to the APU 130. The structure 114 of the fuel line 110 is used to form part of the fuel line 110 and to store aircraft fuel additive 204 or another type of fuel such as SAF. As will be described in more detail below, the arrangement of the aircraft fuel system 100 allows the APU 130 to first consume the contents of structure 114 and then subsequently consume aircraft fuel 202 from fuel tank 120 during operation, by receiving fuel via fuel line 110. This allows the fuel system to directly utilize different fuels at different stages of operation.

[0049] It will be understood that, in the description herein, references to elements “below” other elements refer to the conventional reference frame of an aircraft in a landing position, in which “below” generally corresponds to a direction toward the ground / earth, i.e., in the direction of gravity (e.g., the direction of gravity dictates how a liquid will settle within a volume and thus forms the natural reference frame used to describe the fuel system). Similarly, “above” generally corresponds to a direction away from the ground / earth. Thus, a “horizontal” plane is a plane that is generally parallel to the plane of the ground (e.g., ignoring local surface deformations of the ground), while a vertical plane is a plane perpendicular to the horizontal plane. The “bottom” portion will be understood as being located in the lower portion, and the “top” portion will be understood as being located in the upper portion.

[0050] Figure 2 The fuel line 110, according to the example, is described in further detail. It will also be understood that... Figure 2Although the geometry and form of fuel line 110 are depicted, they are not drawn to scale.

[0051] Fuel conduit 112 is formed by a first fuel conduit 112a connecting the fuel tank 120 to structure 114 and a second fuel conduit 112b connecting structure 114 to APU 130. The exact configuration of fuel conduit 112 will generally vary based on the architecture of the entire fuel system, including the size, shape, and number of parts connecting the fuel tank 120 to the fuel consumption component 130, and therefore, for ease of explanation, this example is a simplified arrangement. However, typically, fuel conduit 112 and structure 114 are arranged sequentially such that fuel is delivered through fuel line 110. In some examples, additional devices or components not shown here as part of fuel line 110 may be present, such as pumps, valves, and / or sensors, operable to monitor and / or control the flow of fluid through fuel line 110.

[0052] Structure 114 is formed by a housing 115a, which contains an internal volume 115b in which fluid can be stored. An inlet 117a disposed in the housing 115a engages with a first fuel conduit 112a, and an outlet 117b disposed in the housing 115a engages with a second fuel conduit 112b. The general direction of fuel flow from fuel tank 120 through fuel line 110 to APU 130 is indicated by arrow F in the figure. The housing 115a is mounted to the surrounding aircraft structure 80 by one or more supports 148, which facilitate the distribution of any stored fuel in structure 114 to, for example, the fuselage frame.

[0053] Compared to fuel conduit 112, structure 114 is a region with increased volume (e.g., per unit length), which allows structure 114 to store a larger volume of fuel compared to fuel conduit 112 of similar length. This is achieved by increasing the cross-sectional area A of structure 114. s The cross-sectional area A of the fuel conduit 112 is greater than that of the fuel conduit 112. c This is achieved. Compared to a fuel conduit 112 of equivalent length (in the direction F of fuel flow), the structure 114 in this example can store more than twice the volume of fluid; in other examples, the structure 114 is sized to store three, five, ten or more times the fuel of the fuel conduit 112.

[0054] It will be understood that the internal volume of structure 114 may depend on the appropriate form that fits structure 114 within, for example, the surrounding aircraft structure and / or the desired function of structure 114. For example, structure 114 may be sized to accommodate approximately 300 liters of additive-fuel blend, for instance, such that structure 114 is configured to store sufficient additive-fuel blend for use by APU 300 to facilitate ground operations of the aircraft, where the APU does not require fuel from fuel tank 120. In other examples, structure 114 may be significantly smaller, such as 5 liters, and may store undiluted aircraft fuel additives to mix with fuel from fuel tank 120. In such examples, it is generally expected that the contents of structure 114 will be used in combination with fuel from fuel tank 120, rather than before the fuel from fuel tank 120. In such an example, structure 114 may be configured such that undiluted aircraft fuel additive is injected into the fuel supply from fuel tank 120 at, for example, a uniform rate or according to, for example, a desired dosing profile, which defines a time-dependent or operation-dependent amount of undiluted aircraft fuel additive to be released into the fuel flow through the fuel line. This can be achieved, for example, actively using a fluid pump component within structure 114, which is operable to cause the stored fuel additive to mix with the fuel flow through the structure. Alternatively or additionally, this can be achieved passively, wherein structure 114 is configured such that the fuel flow through the structure mixes with the stored undiluted aircraft fuel additive, in some examples, for example, without the operation of any fluid pump component, to gradually utilize and deplete the stored undiluted aircraft fuel additive.

[0055] In this example, structure 114 has a tapered inner profile. Therefore, the cross-sectional area A of structure 114 is... s The cross-sectional area gradually increases with distance from inlet 117a and outlet 115b, reaching its maximum at the midpoint between inlet 117a and outlet 115b. Considering the direction F of fuel flow, the cross-sectional area A of structure 114... s The cross-sectional area gradually increases from the inlet 117a, then decreases until it reaches the outlet 117b. This gradual change in cross-sectional area prevents undesirable fluid flow characteristics such as turbulence and air-fluid separation. In some cases, this gradual change is limited to a 6-degree slope (relative to the direction of fuel flow F, which is typically parallel to, for example, the wall of a fuel duct).

[0056] In this example, the internal volume 115b of structure 114 is divided into two regions by a false bottom 140, which is an example of a barrier element 140 configured according to this disclosure. The false bottom 140 is planar and horizontally oriented through structure 114, spanning between the inner walls of housing 115a to substantially divide the interior into two regions. On the first upper side of the false bottom 140 is a first region 144. Fuel flow from inlet 117a to outlet 117b occurs through the first region 144. On the second lower side of the false bottom is a second region 146. The false bottom 140 substantially divides the volume of structure 114 by preventing flow between the two regions 144, 146.

[0057] The guide conduit 142 extends from a location in the second region 146 through the false bottom 140 to a location in the first region 144. As fuel flows through the structure 114, the fuel flow from the second region 146 to the first region 144 via the guide conduit 142 is guided, thereby drawing fuel from the second region 146 and delivering it to the APU 130. In some examples, the second region 146 may be provided with, for example, undiluted additives, and fuel flowing through the first region 144 from the fuel tank 120 may be continuously supplemented with the additives from the second region 146. Pressure balancing devices, such as vents leading from the first region or an external region to the second region, may be included in the structure 114 to backfill the second region and thereby prevent or otherwise mitigate the formation of a vacuum that could otherwise impede fluid flow through the guide conduit 142.

[0058] A refill port 116 is provided in the bottom portion of the housing 115a of structure 114. In this example, the refill port 116 is in fluid communication with a second region 146 of the internal volume 115b and provides a flow path from the outside of the structure into the internal volume 115b, allowing the internal volume 115b to be filled with fluid, and specifically the second region 146 of the internal volume. Therefore, the second region 146 is a fuel storage portion of the internal volume 115b, as the fuel supplied through the refill port 116 is primarily retained within the second region 146.

[0059] A gas release valve 148 is provided inside the top of the housing 115a, and the gas release valve 148 is operable to release gas accumulated in the structure 114 to the outside of the structure. This gas, which may contain a mixture of air and fuel fumes, may be captured and recycled back to the tank, or discharged from the aircraft through vents or buffer tanks on the aircraft. The arrangement of the gas release valve 148 allows the structure 114 to operate as a fuel-air separator device.

[0060] Figure 3The second example of the structure, 114-2, is illustrated. For visual clarity, only a subset of the features are labeled and depicted in the figure.

[0061] In structure 114-2, a barrier element 140-2 is provided according to a second example. In this example, the barrier element 140-2 is a tube having a plurality of through holes 152 disposed within the surface of the barrier element 140-2; Figure 3 In this diagram, only a subset of the through-holes 152 are labeled to aid visual clarity. The through-holes 152 are arranged in a regular distribution across the surface of the barrier element 140-2, and are approximately equidistant and sized. This can provide uniform hydrodynamic properties along the length of the barrier element 140-2. In other examples, for instance, an irregular distribution can be provided to induce specific hydrodynamic behaviors within the structure 114-2.

[0062] Barrier element 140-2 extends from inlet 117a to outlet 177b and is arranged such that the general direction of the fuel flow through structure 114 passes through the central longitudinal axis C of barrier element 140-2. Barrier element 140-2 is sized to match or substantially match (e.g., within 10%) the preceding and / or following conduit portions 112a, 112b. In this way, from the perspective of fuel flowing through fuel conduit 112, barrier element 140-2 serves as an extension of fuel conduit 112 by maintaining the boundary of the fuel flow. Through-holes 152 in the surface of barrier element 140-2 allow fuel stored in the remainder of structure 114 (i.e., outside the barrier element) to pass through, for example, via arrow F. s The indicated route is moved to the general fuel flow path from inlet 117a to outlet 117b.

[0063] A refill port 116-2 is provided in the top portion of structure 114-2. A liquid discharge port 162 is provided in the bottom of structure 114-2, through which the contents of structure 114-2 can be discharged, for example, to perform maintenance or cleaning of structure 114-2.

[0064] Figure 4 The third example of the structure, 114-3, is depicted. Figure 4 In the diagram, axis L is indicated between inlet 117a and outlet 117b. Structure 114-3 has a spherical portion that extends below axis L and constitutes most of the internal volume of structure 114-3. Guide pipe 142-2 extends from outlet 117b into the spherical portion. The geometric center G of structure 114-3 is... c Offset from axis L; although this is only illustrative, it can also be seen in... Figure 2 and Figure 3A similar understanding is recognized in the example. This allows most of the stored fluid to be stored at a relatively low location, which, given the lower center of mass of the stored fluid, can improve the structural stability of structure 114. Furthermore, in Figure 4 In the example, the arrangement of inlet 117a, the spherical portion, and the guide pipe 142-2 can mean that if there is fuel mixed with air in the first fuel conduit 112a, the fuel mixed with air can enter and settle into the reservoir provided by the spherical portion, thereby releasing the air that rises to the top and can be released by the air release valve 148.

[0065] exist Figure 4 In the example, no barrier element is present. Furthermore, in... Figure 4 In the example, a bidirectional refill and discharge port 116-3 is provided at the bottom of structure 114-3, which integrates the refill and discharge functions.

[0066] Figure 5 The illustration shows the modification installation process, in which the aircraft's existing fuel system is modified to become the fuel system according to this disclosure. Specifically, the existing fuel line 75 between the fuel tank 120 and the fuel consumption component 130 includes three fuel conduit sections 112a, 112b, and 112c. The target section 112c is removed and replaced with structure 114, for example, as shown in the diagram. Figures 2 to 4 The described structure 114, 114-2, 114-3 is replaced. Compared to target section 112c, structure 114 has an increased volume and can be used to store fuel additives or other types of fuel supplied to structure 114 by refueling port 116. In this way, an aircraft with an existing fuel system can be modified to implement a multi-fuel fuel system according to this disclosure.

[0067] Figure 6 The illustrations depict additional features that may be included in a fuel system according to this disclosure. Figure 6In the example, a bypass line 195 is provided between the fuel tank 120 and the fuel consumption component 130. This bypass line 195 can be selectively operated to bypass the structure 114, thereby providing an additional fuel flow path from the fuel tank 120 to the fuel consumption component 130. This can be useful when the contents of the structure 114 are preferably stored rather than consumed by the fuel consumption component 130. A fuel scavenging system 197 is also provided, comprising a jet pump or ejector pump operable to cause suction of the contents of the structure 114 from its internal volume, thereby facilitating the removal of the contents from the structure 114, which, for example, can prevent or reduce fuel retention in the reservoir portion of the structure 114. Ensuring that the structure 114 is empty can help balance the weight distribution on the aircraft.

[0068] Figure 7 The illustration shows an aircraft 1000 including a fuel system 100 according to this disclosure. As previously described, the aircraft 1000 is operable to use multiple fuels at different operational phases. The aircraft 1000 can utilize the contents of structure 114 when on the ground, which can reduce unwanted emissions and help maintain local air quality. Similarly, the aircraft 1000 can utilize the contents of structure 1000 during takeoff from an airport and initial climb, during which the aircraft's emissions can still contribute to local air quality, typically measured at an altitude of approximately 1000 meters or 3000 feet above the ground. In later phases, such as when the contents of structure 114 are depleted and / or when the aircraft 1000 is at a sufficiently high altitude, the aircraft 1000 can use conventional aircraft fuel stored in fuel tank 120.

[0069] Figure 8 It is operated by aircraft, such as, in accordance with this disclosure Figure 7 The flowchart is formed by steps S101, S103, and S105 executed in method 500 of aircraft 1000. Method 500 utilizes, for example, the above-mentioned reference Figures 1 to 6 The aircraft fuel system 100 is described. Step S107 is provided as an optional additional step.

[0070] At step S101, aircraft fuel is supplied to the fuel tank 120 of the aircraft fuel system 100. For example, this aircraft fuel may be leftover from previous operations of the aircraft, and therefore supplying aircraft fuel at the fuel tank includes aircraft fuel already stored in the fuel tank. In some examples, step S101 involves receiving aircraft fuel via a fuel tank refueling process, in which aircraft fuel is supplied to the fuel tank through a refueling port. This can correspond to a conventional aircraft refueling process.

[0071] At step S103, an aircraft fuel additive or another aircraft fuel, such as SAF, different from the aircraft fuel provided at step S101, is provided at structure 114 of the fuel line of the aircraft fuel system 100. For example, the aircraft fuel additive may be leftover from previous operation of the aircraft, and therefore providing the aircraft fuel additive or another aircraft fuel at structure 114 includes aircraft fuel additive or another aircraft fuel already stored by structure 114. In some examples, step S103 involves receiving the aircraft fuel additive via a structure refueling process, during which the aircraft fuel additive is provided to the structure through a fluid refueling port of the structure.

[0072] The aircraft fuel additive provided to structure 114 may be provided, for example, in undiluted form or in a blended form in which aircraft fuel is provided in combination with the aircraft fuel additive. Step S103 may involve fully filling structure 114 and at least a portion of fuel conduit 112 with the fuel-additive blend. Step S103 may involve fully filling structure 114 with SAF.

[0073] At step S105, the contents of the structure are consumed by the fuel consumption unit. The contents of the structure are aircraft fuel additives or other aircraft fuel supplied at the structure via the fuel line. For example, the fuel consumption unit consumes aircraft fuel mixed with aircraft fuel additives from the structure. In the case where undiluted fuel additives are stored in the structure, this may involve mixing aircraft fuel from the fuel tank with the fuel additives as aircraft fuel passes through the structure. In the case where the fuel-additive blend is stored in the structure, the fuel-additive blend is extracted from the structure and supplied to the fuel consumption unit. For example, if the structure is substantially fueled with a fuel-additive blend, the fuel consumption unit may consume all the fuel-additive blend stored in the structure before the aircraft fuel from the fuel tank is supplied via the fuel line for the fuel consumption unit's use. For example, step S105 may occur when the aircraft is on the ground.

[0074] At step S107, the fuel consumption component consumes the aircraft fuel from the fuel tank. This occurs later than S105. This can happen when all contents of the structure are depleted. For example, step S107 can occur while the aircraft is in the air.

[0075] It will be understood that, in a general sense, the method includes storing a first type of fuel in a fuel tank, storing a second, different type of fuel or an additive that facilitates the generation of the second, different type of fuel (e.g., by forming a blend of the additive and conventional aircraft fuel) in a structure within the fuel line, and supplying the first type of fuel and the second, different type of fuel or the additive that facilitates the generation of the second, different type of fuel to a fuel consumption component. The first type of fuel and the second, different type of fuel or the additive that facilitates the generation of the second, different type of fuel can be consumed such that: first, the contents of the structure are consumed, and then, subsequently, the contents of the fuel tank are consumed. Alternatively, the first type of fuel and the second, different type of fuel or the additive that facilitates the generation of the second, different type of fuel can be consumed such that the contents of the structure and the contents of the fuel tank are consumed simultaneously.

[0076] The above embodiments should be understood as illustrative examples of the present invention. Other embodiments of the present invention are contemplated.

[0077] For example, in the illustrated embodiment, the aircraft's APU is a fuel-consuming component. In other examples, one or more of the aircraft's engines may be fuel-consuming components. For example, the structure's contents may be usable during takeoff and initial climb.

[0078] For example, the examples illustrated in this disclosure primarily relate to aircraft fuel additives stored in the structure in the form of undiluted or fuel-additive blends. However, it will be understood that in other examples, SAFs may be stored in the structure without, for example, aircraft fuel additives, while facilitating multi-fuel operations as previously described.

[0079] In some examples, multiple structures are arranged, each on a corresponding fuel line of a fuel-consuming component. In this way, for example, each fuel-consuming component can simultaneously use the contents of its respective structure during the initial operation phase.

[0080] For example, the structure could be geometrically similar to a pipe or conduit, albeit enlarged to have a larger cross-sectional area. That is, the structure could be essentially tubular, for example, with a hole having a larger diameter than the holes in the preceding and following piping systems, and the structure could be provided with refueling ports to allow aircraft fuel additives to be supplied into the structure.

[0081] The structure may include additional features that help increase storage capacity. For example, a branching piping system as part of the structure can increase the structure's storage capacity (e.g., simply by providing multiple sections that can store and transport fuel). Similarly, loops or other devices that generate tortuous paths for fluids can increase storage capacity by providing an increased total path.

[0082] Two or more structures can be sequentially arranged along the pipeline to facilitate the described method. This can be useful, for example, where the size of each structure is limited by the surrounding aircraft structure, and thus providing two or more structures can facilitate an overall increase in volume to achieve, for example, a total volume suitable for the desired operating time range, while each structure remains relatively limited in size.

[0083] It should be understood that any feature described with respect to any embodiment may be used alone or in combination with other described features, and may also be used in combination with one or more features of any other embodiment or any combination of embodiments. Furthermore, equivalents and modifications not described above may be employed without departing from the scope of the invention as defined in the appended claims. It should be noted that, unless expressly stated otherwise, the term "or" as used herein should be interpreted as meaning "and / or".

Claims

1. An aircraft fuel system, comprising: A fuel line configured to fluidly connect a fuel tank to a fuel consumption component, wherein the fuel line includes the following components for fluidly connecting the fuel tank to the fuel consumption component: Fuel conduit, and The structure is fluidly connected to the fuel conduit. The structure includes inlet and outlet for conveying aircraft fuel from the fuel tank to the fuel consumption component through the internal volume of the structure, wherein the cross-sectional area of ​​the internal volume of the structure is larger than the internal cross-sectional area of ​​the fuel conduit. The structure includes a fluid refill port that fluidly connects the interior of the structure to the exterior of the structure, and fluid can be supplied to the structure through the fluid refill port.

2. The aircraft fuel system according to claim 1, wherein, The cross-sectional area of ​​the structure is greater than twice the cross-sectional area of ​​the fuel conduit, or optionally, the cross-sectional area is greater than three times the cross-sectional area of ​​the fuel conduit.

3. The aircraft fuel system according to claim 1 or claim 2, wherein, The structure has a volume of more than 100 liters, and optionally, the volume exceeds 300 liters.

4. The aircraft fuel system according to any one of the preceding claims, wherein, The structure includes a gas release valve operable to release gas from the internal volume of the structure to the outside of the structure, optionally wherein the gas release valve is disposed in the top portion of the structure.

5. The aircraft fuel system according to any one of the preceding claims, wherein, The structure also includes a liquid discharge port through which liquid within the structure can be released to the outside of the structure. Optionally, the liquid discharge port and the fluid refill port are integrally combined to form a bidirectional liquid port.

6. The aircraft fuel system according to any one of the preceding claims, wherein, The internal volume of the structure has a cross-sectional area that gradually changes along the main fuel flow direction through the structure.

7. The aircraft fuel system according to any one of the preceding claims, wherein, The structure includes a barrier element located within the internal volume of the structure, the barrier element forming at least a portion of the boundary between a first region and a second region of the internal volume, wherein, in use, a majority of the main fuel flow from the inlet to the outlet passes through the first region.

8. The aircraft fuel system according to claim 7, wherein, The barrier element is perforated, allowing fluid to move from the second region to the first region, wherein, optionally, the barrier element is a perforated conduit extending between the inlet and the outlet.

9. The aircraft fuel system according to claim 7 or 8, wherein, The structure includes a guide conduit extending from the second region through the barrier element to the first region, thereby providing a fluid path from the second region to the first region.

10. The aircraft fuel system according to any of the preceding claims, wherein, The geometric center of the structure is offset from the axis extending from the inlet to the outlet.

11. The aircraft fuel system according to claim 10, wherein, Most of the internal volume of the structure is located below the axis.

12. The aircraft fuel system according to claim 11 when dependent on any one of claims 7 to 9, wherein, The axis extending from the inlet to the outlet intersects the first region, and the second region forms most of the volume of the structure.

13. The aircraft fuel system according to any of the preceding claims, wherein, The fuel conduit includes a first fuel pipe and a second fuel pipe, the structure fluidly connecting the first fuel pipe to the second fuel pipe, and the series connection of the first fuel pipe, the structure and the second fuel pipe thereby fluidly connecting the fuel tank to the fuel consumption component.

14. An aircraft comprising an aircraft fuel system according to any of the preceding claims, the aircraft including the fuel line, the fuel tank, and the fuel consumption component.

15. The aircraft according to claim 14, wherein, The fuel tank stores aircraft fuel, and the structure of the fuel pipeline stores aircraft fuel additives or another type of aircraft fuel different from the aircraft fuel stored in the fuel tank.

16. The aircraft according to claim 15, wherein, The structure of the fuel pipeline stores a blend of aircraft fuel and aircraft fuel additives.

17. The aircraft according to any one of claims 14 to 16, wherein, The fuel-consuming component is the auxiliary power unit of the aircraft.

18. A method of operating an aircraft, comprising: The aircraft is fueled at its fuel tank. The fuel line provides (i) another aircraft fuel different from the aircraft fuel provided at the fuel tank of the aircraft and / or (ii) an aircraft fuel additive at a structure of the fuel line, the fuel line fluidly connecting the fuel tank to a fuel consumption component; as well as The fuel consumer consumes (i) another aircraft fuel from the structure and / or (ii) aircraft fuel from the structure mixed with the aircraft fuel additive.

19. The method according to claim 18, wherein, Providing aircraft fuel at the fuel tank of the aircraft includes receiving aircraft fuel through a fuel tank refueling process, during which aircraft fuel is supplied to the fuel tank through the refueling port of the fuel tank; and / or Providing (i) the other aircraft fuel and / or (ii) the aircraft fuel additive at the structure of the fuel line includes receiving the other aircraft fuel and / or the aircraft fuel additive respectively through a structure refueling process, wherein the other aircraft fuel and / or the aircraft fuel additive is supplied to the structure through a fluid refueling port of the structure during the structure refueling process.

20. The method according to claim 18 or 19, wherein, The fuel consumer is an auxiliary power unit, and / or at the moment the aircraft is on the ground.

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