JP6706085B2 - Fuel supply system, fuel supply method and aircraft - Google Patents

Description

Embodiments of the present invention relate to a fuel supply system, a fuel supply method, and an aircraft.

Conventionally, integral tanks and bladder tanks are known as fuel tanks used in aircraft.

The integral tank uses an aircraft structure itself, such as a main wing and a fuselage, whose watertightness is improved by a sealant (sealing agent), as a fuel tank. When an integral tank is used as the fuel tank, the aircraft structure such as the wing and the fuselage and the fuel tank can be integrated, and it is not necessary to provide a dedicated fuel tank. Therefore, the weight of the aircraft is reduced and the structure of the aircraft is simplified. In addition, when the integral tank is used as the fuel tank, the amount of fuel to be loaded in the size of the fuel tank can be increased.

However, when using an integral tank as a fuel tank for a small unmanned aerial vehicle in which the wing and the fuselage are designed integrally, the flexibility of sealing work and fastener selection in the fuel tank to prevent fuel leakage decreases. , Is a factor that increases the manufacturing cost of small unmanned aerial vehicles.

On the other hand, a bladder tank stores a bag-shaped container (bladder) made of an elastic body such as synthetic rubber inside an aircraft structure such as a main wing or a fuselage and uses it as a fuel tank (for example, Patent Document 1). And Patent Document 2). When the bladder tank is used as the fuel tank, there is an advantage that it is difficult for air, which is an impurity, to flow into the fuel tank. Further, when the bladder tank is used as the fuel tank, it is not necessary to seal the inside of the fuel tank.

Further, when using the bladder tank, there is an advantage that the position of the center of gravity can be controlled. As a specific example, we propose a technology that adjusts the movement of the center of gravity of the aircraft by installing multiple bladder tanks so that it can be pressurized with hot air and controlling the opening and closing of valves for discharging fuel from each bladder tank. Has been done.

However, when a bladder tank is used as a fuel tank for an aircraft, in order to uniformly discharge the fuel from the bladder tank, it is necessary to inject outside air, exhaust gas, or the like between the fuselage and the fuel tank to pressurize the fuel tank. Therefore, in addition to the fuel tank, a device having a complicated structure for uniformly pressurizing the fuel tank and a complicated control are required.

JP, 9-242611, A US Patent No. 8757549

When flying an aircraft, it is important to suppress the movement of the center of gravity of the airframe.

However, when an integral tank is used as a fuel tank for an aircraft, there is a problem that the center of gravity of the entire body moves due to the movement of the fuel as the fuel is consumed, making flight control difficult.

On the other hand, when a plurality of bladder tanks are installed and the center of gravity of the aircraft is adjusted by adjusting the amount of fuel discharged from each bladder tank, there is a problem that the configuration of the piping system for discharging fuel becomes complicated. .. Further, since a plurality of bladder tanks are installed, it is necessary to refill the fuel as many times as the number of bladder tanks.

Therefore, an object of the present invention is to reduce the amount of movement of the center of gravity of an aircraft due to fuel consumption with a simpler configuration.

A fuel supply system according to an embodiment of the present invention uses a flexible fuel tank for an aircraft to store fuel, and a pressure distribution determined according to the position of the center of gravity of the aircraft in which the fuel tank is mounted. And a pressurization system for discharging the fuel from the fuel tank by pressurizing the fuel tank , the pressurization system comprising a first pressurization system of the fuel tank located away from a center of gravity of the aircraft. To pressurize a portion with a first pressure, while pressurizing a second portion closer to the first portion from the position of the center of gravity of the aircraft with a second pressure lower than the first pressure. Ru is configured.
The fuel supply method according to the embodiment of the present invention is a fuel supply method for discharging the fuel from the fuel tank by pressurizing a flexible fuel tank for an aircraft for storing fuel, by pressure of the fuel tank at the determined pressure distribution depending on the position of the center of gravity of the aircraft equipped with the fuel tank, a first portion of the fuel tank in a position away from the position of the center of gravity of the aircraft first while pressurized with first pressure, and so that the pressure of the second portion is closer than the first portion at a second pressure lower than the first pressure from the position of the center of gravity of the aircraft It is a thing.
An aircraft according to the embodiment of the present invention includes the above-described fuel supply system.

The block diagram of the aircraft provided with the fuel supply system which concerns on the 1st Embodiment of this invention. The block diagram of the aircraft provided with the fuel supply system which concerns on the 2nd Embodiment of this invention. The figure explaining an example of the control method of the pressure by the pressure regulation system shown in FIG. An example in which the spring constant of each elastic body can be variably controlled when pressure is applied to the fuel tank composed of the first sub-tank, the second sub-tank and the third sub-tank by a plurality of elastic bodies Fig. The block diagram of the aircraft provided with the fuel supply system which concerns on the 3rd Embodiment of this invention. The block diagram of the aircraft provided with the fuel supply system which concerns on the 4th Embodiment of this invention.

A fuel supply system, a fuel supply method, and an aircraft according to embodiments of the present invention will be described with reference to the accompanying drawings.

(First embodiment)
(Structure and function)
FIG. 1 is a configuration diagram of an aircraft including a fuel supply system according to a first embodiment of the present invention.

The fuel supply system 1 is a device included in the aircraft 2. The fuel supply system 1 includes a fuel tank 3 for storing fuel and a pressurizing system 4 for discharging the fuel from the fuel tank 3.

The fuel tank 3 is a flexible bladder tank for the aircraft 2. The bladder tank is made of an elastic body such as synthetic rubber that does not deteriorate even if it contacts aviation fuel. FIG. 1 shows an example in which the aircraft 2 is a small unmanned aerial vehicle. A bladder tank used for a small unmanned aerial vehicle is installed inside a body having a substantially cylindrical structure. Normally, the fuel in the bladder tank is not used up and the fuel always remains. For this reason, the bladder tank used for small unmanned aerial vehicles is not normally replaced, but the bladder tank is refilled with fuel.

Of course, the fuel tank 3 may be mounted on a small or large manned aircraft such as a fixed-wing aircraft. When the fuel tank 3 is mounted on a large machine, the fuel tank 3 can be mounted inside the main wing.

The pressurizing system 4 is a system for discharging fuel from the fuel tank 3 by externally pressurizing the fuel tank 3. In particular, the pressurization system 4 is configured to pressurize the fuel tank 3 with a pressure distribution determined according to the position of the center of gravity G of the body of the aircraft 2 in which the fuel tank 3 is mounted.

During the flight of the aircraft 2, it is important to reduce the movement of the center of gravity G of the airframe due to fuel consumption. For example, in the case of a small unmanned aerial vehicle in which a bladder tank is housed inside the body, the center of gravity G may move downward due to a decrease in fuel, and the body may tilt.

Therefore, the pressurization system 4 is configured to pressurize the fuel tank 3 with a pressure distribution that is determined so that the amount of movement of the position of the center of gravity G of the airframe of the aircraft 2 due to fuel consumption is reduced. Specifically, the fuel tank 3 is pressurized with a high pressure at a position away from the position of the center of gravity G of the aircraft 2, while the fuel tank 3 is pressurized with a low pressure at a position near the position of the center of gravity G of the aircraft 2. can do.

Then, the fuel will be reduced from the portion away from the position of the center of gravity G of the aircraft 2. Therefore, even if the fuel is reduced, the position of the center of gravity of the fuel can be kept as close to the position of the center of gravity G of the aircraft 2 as possible. As a result, the amount of movement of the position of the center of gravity G of the aircraft 2 that accompanies fuel consumption can be reduced.

Therefore, the pressurizing system 4 has a plurality of pressurizing mechanisms 5. The pressurizing system 4 is configured to pressurize different parts of the fuel tank 3 with different pressures by using the plurality of pressurizing mechanisms 5.

For example, when the fuel tank 3 is pressurized with at least two types of pressure, the first portion of the fuel tank 3 is pressurized with the first pressure by the pressurization mechanism 5, while the first portion of the fuel tank 3 is The second part different from the first part is pressurized by another pressurizing mechanism 5 with a second pressure lower than the first pressure. In this case, in order to reduce the amount of movement of the center of gravity G of the aircraft 2 that accompanies fuel consumption, the first portion located farther than the second portion from the position of the center of gravity G of the airframe of the aircraft 2 is raised. While pressurizing with the first pressure, it is possible to pressurize the second part, which is closer to the first part than the position of the center of gravity G of the airframe of the aircraft 2, with the second pressure lower than the first pressure. is necessary.

That is, the first portion and the second portion of the fuel tank 3 to which the first pressure and the second pressure are applied are determined based on the distance from the position of the center of gravity G of the aircraft 2 in which the fuel tank 3 is mounted. be able to. Specifically, the first portion of the fuel tank 3 and the first portion of the fuel tank 3 are set so that the distance from the center of gravity G of the first portion of the fuel tank 3 is larger than the distance from the center of gravity G of the second portion of the fuel tank 3. The second part can be determined. The center of gravity G of the aircraft 2 may be, for example, the center of gravity when the fuel tank 3 is filled with fuel, or the center of gravity when the fuel tank 3 is filled with an average amount of fuel.

As described above, the portion of the fuel tank 3 having a higher priority is determined based on the distance from the center of gravity G of the machine body, and the portion farther from the center of gravity G of the machine body is preferentially pressurized with a higher pressure. Multiple pressurization mechanisms 5 can be designed.

As a specific example, as shown in FIG. 1, if the aircraft 2 is a small unmanned aerial vehicle, the fuel tank 3 is arranged at a position in the fuselage that overlaps the center of gravity G of the airframe. Therefore, the pressurizing system 4 pressurizes the first portions on both sides of the fuel tank 3 away from the center of gravity G of the machine body with a relatively high first pressure, while the pressure of the fuel tank 3 near the center of gravity G of the machine body is increased. The central second portion may be configured to be pressurized with a second pressure that is relatively lower than the first pressure.

When pressurizing different parts of the fuel tank 3 with different pressures using the plurality of pressurizing mechanisms 5, the structure of the fuel tank 3 can be a structure in which a plurality of sub-tanks 6 are connected. In this case, the plurality of pressurization mechanisms 5 can be used to pressurize the plurality of sub-tanks 6 at a pressure determined for each sub-tank 6. That is, if the fuel tank 3 is divided into a plurality of sub tanks 6, it becomes possible to separate a plurality of portions of the fuel tank 3 to which different pressures are applied from each other. Moreover, it becomes easy to regulate the pressing direction of each pressing mechanism 5.

Further, when the structure of the fuel tank 3 is a structure in which a plurality of sub tanks 6 are connected, it is necessary that the fuel discharge port 7 is provided only in one of the plurality of sub tanks 6 for supplying fuel to the engine 8. This is preferable from the viewpoint of simplifying the configuration. Particularly, in the case of a rocket type small unmanned aerial vehicle, the number of engines 8 is one. Therefore, if the number of the discharge ports 7 of the fuel tank 3 is set to one, the fuel tank 3 and the engine 8 can be connected using a single supply pipe without providing a junction. Of course, even if the aircraft 2 has a plurality of engines 8, if the fuel tank 3 is mounted for each engine 8, the number of the discharge ports 7 of the fuel tank 3 should be one. Thus, the fuel piping structure can be simplified.

Conversely, the discharge port 7 may be provided for each sub tank 6. In that case, the fuel supply pipes connected to the plurality of sub-tanks 6 are connected to each other. Further, when the discharge port 7 is provided for each sub-tank 6, it is not always necessary to connect the sub-tanks 6 to each other.

In the example shown in FIG. 1, the fuel tank 3 has a structure in which three sub-tanks 6 of a first sub-tank 6A, a second sub-tank 6B, and a third sub-tank 6C are arranged in the traveling direction of the aircraft 2. That is, the second sub tank 6B is arranged at a position overlapping the center of gravity G of the aircraft 2, and the first sub tank 6A and the third sub tank 6C are arranged on both sides of the second sub tank 6B. The discharge port 7 is provided only in the central second sub-tank 6B. Since the fuel collects downward due to gravity, the discharge port 7 is formed on the bottom surface of the second sub tank 6B.

The first sub-tank 6A, the second sub-tank 6B, and the third sub-tank 6C are practically installed in the casing 9 from the viewpoint of restricting the pressurizing direction of each sub-tank 6 by the pressurizing mechanism 5. The shape of each sub-tank 6 is arbitrary, but if each sub-tank 6 is stored in the fuselage of the aircraft 2, for example, a substantially columnar shape having the longitudinal direction in the front-rear direction of the aircraft 2 according to the shape of the fuselage is used. It can be shaped. Therefore, it is rational that the shape of the casing 9 also fits the sub tank 6.

However, it is necessary to provide the casing 9 with an opening for pressurizing the upper surface side of the sub-tank 6 by the pressurizing mechanism 5. Therefore, the casing 9 can be formed of, for example, a rigid body whose upper surface is open and whose lower surface is a part of a cylinder. As the material of the casing 9, a light material having a required strength such as a composite material, aluminum or resin can be used.

When one discharge port 7 common to the first sub tank 6A, the second sub tank 6B, and the third sub tank 6C is provided, the first sub tank 6A, the second sub tank 6B, and the third sub tank 6C are discharged from each other. It is necessary to connect at a lower position close to 7. Therefore, holes or slits may be provided in the casing 9 to connect the sub tanks 6 to each other.

When forming a slit in the casing 9, the sub-tanks 6 can be connected to each other by a flat flow path passing through the slit. On the other hand, when the through hole is formed in the casing 9, the sub tanks 6 can be connected by the pipe 10 as illustrated in FIG. 1. Therefore, the fuel tank 3 may be manufactured as a bladder tank having a special shape in which a plurality of sub tanks 6 are connected, or by forming a connection port in a plurality of bladder tanks having a simple shape and connecting them by a pipe 10. May be made.

When the flow paths between the sub-tanks 6 are narrow as in the case where the sub-tanks 6 are connected to each other by the pipe 10, it is realistic to provide the fuel replenishment port 11 in each sub-tank 6. However, if the flow path between the sub-tanks 6 is sufficiently wide and fuel can be replenished using the flow path between the sub-tanks 6, a common replenishment port 11 may be provided for the plurality of sub-tanks 6. The fuel replenishing port 11 can be provided at a position above the sub tank 6 where it does not interfere with the pressurizing mechanism 5.

An elastic body 12 such as a spring or rubber can be used for the pressurizing mechanism 5 that pressurizes the upper surface of the sub tank 6 from the opening of the casing 9. That is, the pressurizing system 4 can be configured to pressurize the sub-tanks 6 of the fuel tank 3 with different pressures by using the plurality of elastic bodies 12. The material of the elastic body 12 is arbitrary, but it is inappropriate to use a toxic substance such as lead or a flammable substance such as magnesium as the material of the elastic body 12.

As shown in FIG. 1, when the fuel tank 3 is composed of the second sub-tank 6B overlapping the center of gravity G and the first sub-tank 6A and the third sub-tank 6C on both sides, the fuel tank 3 is separated from the center of gravity G of the airframe. The first sub-tank 6A and the third sub-tank 6C are determined to be the first parts that are pressurized at a relatively high first pressure, while the second sub-tanks 6B are pressurized at a relatively low second pressure. It can be decided in two parts.

Then, the first elastic body 12A having the first spring constant is used, and the first sub-tank 6A and the third sub-tank 6C which are determined as the first portion of the fuel tank 3 are relatively high. It can be pressurized with the pressure of. On the other hand, by using the second elastic body 12B having the second spring constant smaller than the first spring constant, the first second sub-tank 6B determined as the second portion of the fuel tank 3 It can be pressurized at a second pressure lower than the pressure. That is, the spring constant of the elastic body 12 corresponding to the portion of the fuel tank 3 having a high pressurization priority is made larger than the spring constant of the elastic body 12 corresponding to the portion of the fuel tank 3 having a low pressurization priority. be able to.

As a result, the first sub-tank 6A and the third sub-tank 6C, which are separated from the center of gravity G of the aircraft 2, are crushed first by the first elastic bodies 12A having relatively large spring constants, while the center of gravity G of the aircraft 2 is changed. The second central sub tank 6B can be finally crushed by the second elastic body 12B having a relatively small spring constant. As a result, the amount of movement of the center of gravity of the fuel tank 3 and the amount of movement of the center of gravity G of the aircraft 2 due to fuel consumption can be reduced.

The upper surface of each sub-tank 6 against which the elastic body 12 is pressed has a curved surface substantially similar to the side surface of a cylinder. Therefore, as shown in FIG. 1, a pressing plate 13 may be provided at the end of each elastic body 12, and the pressing plate 13 may be pressed against the upper surface of each sub tank 6.

The spring constant of each elastic body 12 can be empirically determined by an actual test. Alternatively, the spring constant of each elastic body 12 can be determined by simulation. When the spring constant is determined by simulation, for example, the optimum spring constant can be obtained by optimization calculation that minimizes the amount of movement of the center of gravity G of the aircraft 2 using the spring constant as a parameter. For the optimization calculation for obtaining the optimum spring constant, the size and shape of each sub-tank 6, the contact area between each elastic body 12 and each sub-tank 6, the allowable range of the amount of movement of the center of gravity G of the aircraft 2, the sub-tank 6 The structure of the connecting portion or the like can be used.

The fuel supply system 1 as described above is configured such that different portions of the fuel tank 3 can be pressurized with different pressures so that the amount of movement of the center of gravity G of the aircraft 2 due to fuel consumption is reduced. Therefore, the fuel tank 3 is divided into a plurality of sub-tanks 6, and each sub-tank 6 is provided with a priority order so that the elastic body 12 can pressurize.

(effect)
Therefore, according to the fuel supply system 1, it is possible to reduce the amount of movement of the center of gravity G of the aircraft 2 due to fuel consumption. Further, by using the elastic body 12 to pressurize the fuel tank 3, it is possible to eliminate the need for a system for taking in outside air or exhaust air for pressurization. As a result, the structure of the fuel tank 3 can be simplified. Further, if the fuel tank 3 is divided into a plurality of sub-tanks 6 and a common discharge port 7 is provided, each sub-tank 6 is pressurized at a desired pressure, while the fuel between the fuel tank 3 and the engine 8 is discharged. The piping system can be simplified.

(Second embodiment)
FIG. 2 is a configuration diagram of an aircraft including a fuel supply system according to a second embodiment of the present invention.

In the fuel supply system 1A according to the second embodiment shown in FIG. 2, air is used instead of the elastic body 12 to pressurize the fuel tank 3, and the pressure distribution applied to the fuel tank 3 is adjusted. The point that it is possible is different from the fuel supply system 1 in the first embodiment. Other configurations and operations of the fuel supply system 1A in the second embodiment are substantially the same as those of the fuel supply system 1 in the first embodiment, and therefore, the same configurations or corresponding configurations are designated by the same reference numerals. The description is omitted.

The pressurization system 4 of the fuel supply system 1A in the second embodiment has an air extraction pipe 20 and an air compressor 21 in addition to the plurality of pressurization mechanisms 5A. Further, the fuel supply system 1A can be provided with a pressure adjusting system 22 as required.

Each pressurizing mechanism 5A of the fuel supply system 1A includes a pressurizing container 23, an air supply port 24, a supply air control valve 25, an air exhaust port 26, and an exhaust air control valve 27. The sub-tank 6 is housed inside each pressurizing container 23.

The air bleeder pipe 20 is a pipe for taking in air for pressurizing the plurality of sub-tanks 6 forming the fuel tank 3. Examples of the air for pressurizing the fuel tank 3 include compressed air before combustion in the engine 8 as well as outside air. Therefore, when the outside air is used as the air for pressurizing the fuel tank 3, one end of the air extraction pipe 20 is arranged at a position where the outside air can be taken in. On the other hand, when the compressed air before combustion in the engine 8 is used as the air for pressurizing the fuel tank 3, one end of the air extraction pipe 20 is arranged at a position where the compressed air before combustion can be taken.

The air compressor 21 is provided as needed when the pressure of the air extracted by the air extraction pipe 20 is insufficient to pressurize the fuel tank 3. In the air compressor 21, the pressure of the air extracted by the air extraction pipe 20 is increased to the pressure required to pressurize the fuel tank 3.

The air extraction pipe 20 connected to the output side of the air compressor 21 is branched and connected to the air supply port 24 attached to each pressurizing container 23. A supply air control valve 25 is provided at each air supply port 24 to control the flow rate of air into the pressurized container 23. On the other hand, an air outlet 26 is attached to each pressure vessel 23. A discharge air control valve 27 is provided at each air discharge port 26 to control the flow rate of the air discharged from the pressurized container 23.

Therefore, by adjusting the opening degree of at least one of the supply air control valve 25 and the discharge air control valve 27 attached to each pressurizing container 23, each pressurization determined by the difference between the inflow amount and the discharge amount of air. The pressure of air in the container 23 can be changed between the pressurized containers 23. This makes it possible to independently pressurize the plurality of sub-tanks 6 at a desired pressure. That is, by changing the pressure of the air that has flowed into the space between the rigid pressure vessel 23 and the flexible sub-tank 6 between the pressure vessels 23, the plurality of sub-tanks 6 are pressurized with different pressures. be able to.

As shown in FIG. 2, when the fuel tank 3 is composed of the second sub-tank 6B overlapping the center of gravity G and the first sub-tank 6A and the third sub-tank 6C on both sides, the fuel tank 3 is separated from the center of gravity G of the airframe. The first sub-tank 6A and the third sub-tank 6C are determined to be the first parts that are pressurized at a relatively high first pressure, while the second sub-tanks 6B are pressurized at a relatively low second pressure. It can be decided in two parts.

Therefore, by adjusting the opening degree of at least one of the supply air control valve 25 and the exhaust air control valve 27, the first sub-tank determined as the first portion of the fuel tank 3 using the first amount of air. 6A and the third sub-tank 6C can be pressurized with a relatively high first pressure. On the other hand, the second pressure lower than the first pressure with respect to the central second sub-tank 6B determined as the second portion of the fuel tank 3 using the second amount of air smaller than the first amount. It can be pressurized with pressure. That is, the amount of air supplied to the portion of the fuel tank 3 having a high pressurization priority can be made larger than the amount of air supplied to the portion of the fuel tank 3 having a low pressurization priority.

As a result, the first sub-tank 6A and the third sub-tank 6C that are distant from the center of gravity G of the aircraft 2 are first crushed by the relatively large first amount of air, respectively, while the center of the aircraft 2 near the center of gravity G is The second sub tank 6B can be finally crushed with a relatively small second amount of air. As a result, the amount of movement of the center of gravity of the fuel tank 3 and the amount of movement of the center of gravity G of the aircraft 2 due to fuel consumption can be reduced.

Even when each of the plurality of sub-tanks 6 is housed in the pressurized container 23, the fuel can be supplied to the engine 8 from the single exhaust port 7 by connecting the plurality of sub-tanks 6 to each other. In that case, a through hole or a slit is provided in the pressure vessel 23, and the plurality of sub-tanks 6 can be connected to each other by a flow path such as the pipe 10 passing through the through hole or the slit of the pressure vessel 23. However, the pressure in each pressurizing container 23 can be more accurately set by not forming a gap through which air leaks between the through hole or slit of the pressurizing container 23 and the flow path connecting the plurality of sub-tanks 6. Is important from the perspective of controlling.

The openings of the supply air control valve 25 and the exhaust air control valve 27 may be adjusted in advance before the flight of the aircraft 2, and the openings may be fixed during the flight. However, if the opening degree of at least one of the supply air control valve 25 and the exhaust air control valve 27 is variably controlled during flight of the aircraft 2, the fuel is distributed with a more appropriate pressure distribution in order to reduce the movement amount of the center of gravity G of the aircraft 2. It is possible to pressurize the tank 3.

Therefore, it is possible to provide the pressure adjustment system 22 that adjusts the distribution of pressure applied to the fuel tank 3 by controlling the opening degree of at least one of the supply air control valve 25 and the exhaust air control valve 27. The pressure adjusting system 22 generates a control signal for controlling the opening degree of at least one of the supply air control valve 25 and the discharge air control valve 27, and uses the generated control signal as the supply air control valve 25 and the discharge air control valve 27. Of at least one of the above. The control signal can be generated as an air signal or an electric signal.

The components of the pressure regulation system 22 that process electric signals can be configured by electric circuits. In particular, the component that processes digital information can be configured by an electronic circuit that causes a computer to read a program. On the other hand, the components of the pressure control system 22 that process the air signal may be configured by an air circuit.

When the amount of fuel in the sub tank 6 decreases as the fuel is consumed, the size of the sub tank 6 decreases. Therefore, when the difference between the supply amount of air into each pressurizing container 23 and the discharge amount of air from each pressurizing container 23 is constant, the air pressure in each pressurizing container 23 consumes fuel. It will decrease with.

Therefore, the pressure adjustment system 22 controls the opening degree of at least one of the supply air control valve 25 and the discharge air control valve 27 so that the decrease in the air pressure in each pressurized container 23 due to the fuel consumption is suppressed. Can be controlled. Further, even if the size of the sub-tank 6 and the amount of fuel remaining in the sub-tank 6 change, the amount of movement of the center of gravity G of the aircraft 2 is reduced, and a proper flow rate of fuel is supplied to the engine 8. The opening degree of at least one of the supply air control valve 25 and the discharge air control valve 27 can be controlled by the pressure adjustment system 22 so that an appropriate pressure is applied to the sub tank 6.

In order to suppress the decrease in the air pressure in each pressurizing container 23 due to the fuel consumption, the opening degree of the supply air control valve 25 is gradually increased as the fuel consumption increases to increase the pressure. The amount of air discharged from each pressurizing container 23 is reduced by controlling to increase the amount of air supplied to the container 23 and gradually decreasing the opening of the discharge air control valve 27 as the amount of fuel consumption increases. It suffices to perform at least one of the controls.

The control of the opening degree of at least one of the supply air control valve 25 and the discharge air control valve 27 can be performed by the pressure adjustment system 22 by a control program created in advance by performing a test or a simulation. That is, the change over time of the opening degree of at least one of the supply air control valve 25 and the discharge air control valve 27 can be determined in advance, and control for changing the opening degree with time can be performed. For example, it is possible to perform control to gradually increase the opening degree of the supply air control valve 25 and control to gradually decrease the opening degree of the discharge air control valve 27 using the flight time of the aircraft 2 as a parameter. In this case, the control algorithm becomes very simple.

Alternatively, in order to control the pressure in each pressurizing container 23 with higher accuracy, the fuel consumption amount or the fuel residual amount is measured, and based on the fuel consumption amount or the fuel residual amount obtained by the measurement. It is also possible to control the pressure in each pressurizing container 23. It is also possible to measure the pressure in each pressurizing container 23 and perform feedback control or feedforward control to bring the measured pressure value closer to the pressure control value.

When performing pressure control based on the fuel consumption amount or the remaining amount, a sensor necessary for measuring the fuel consumption amount or the remaining amount is provided. Further, when performing feedback control or feedforward control of the pressure in each pressure vessel 23, a sensor necessary to measure the pressure in each pressure vessel 23 is provided.

FIG. 3 is a diagram illustrating an example of a pressure control method by the pressure adjustment system 22 shown in FIG.

In FIG. 3, fuel flowmeters 30A, 30B, 30C and air pressure gauges 31A, 31B, 31C are attached to respective parts of the fuel tank 3, and the measured values of the flowmeters 30A, 30B, 30C and pressure gauges 31A, 31B, 31C are shown. An example in which the pressure adjustment system 22 controls the opening degrees of the supply air control valve 25 and the discharge air control valve 27 on the basis of FIG.

More specifically, the fuel flow path between the first sub tank 6A and the second sub tank 6B, the fuel flow path between the third sub tank 6C and the second sub tank 6B, and the second sub tank. Flowmeters 30A, 30B, 30C are attached to the fuel flow paths from the discharge port 7 of 6B to the engine 8, respectively. Therefore, the flow rate of fuel discharged from the first sub tank 6A and flowing into the second sub tank 6B, the flow rate of fuel discharged from the third sub tank 6C and flowing into the second sub tank 6B, and the second sub tank 6B The flow rate of the discharged fuel can be measured.

Further, a pressure gauge 31A for measuring the pressure of air between the first sub-tank 6A and the pressure vessel 23, a pressure gauge 31A for measuring the pressure of air between the second sub-tank 6B and the pressure vessel 23. A pressure gauge 31B and a pressure gauge 31C for measuring the pressure of air between the third sub-tank 6C and the pressure vessel 23 are attached. Therefore, the pressure of the air loaded on the first sub tank 6A, the second sub tank 6B, and the third sub tank 6C can be measured.

The detected value of the flow rate of fuel measured by each of the flow meters 30A, 30B and 30C and the detected value of the pressure measured by each of the pressure gauges 31A, 31B and 31C are output to the pressure adjustment system 22 as detection signals.

If the discharge amount of fuel from the first sub-tank 6A, the second sub-tank 6B and the third sub-tank 6C and the amount of fuel flowing into the second sub-tank 6B can be measured by the flowmeters 30A, 30B and 30C, It is possible to obtain the amount of fuel used and the amount of fuel remaining in the sub tank 6A, the second sub tank 6B, and the third sub tank 6C. Therefore, in the pressure control system 22, the first sub-tank 6A and the second sub-tank 6B are determined based on the amount of fuel used or the remaining amount in the first sub-tank 6A, the second sub-tank 6B and the third sub-tank 6C. Also, the control value of the pressure of the air to be loaded on the third sub tank 6C can be determined.

For example, as the amount of fuel used increases and the amount of remaining fuel decreases, the control value of the pressure of air to be loaded on the first sub-tank 6A, the second sub-tank 6B and the third sub-tank 6C is increased. You can Alternatively, the control value of the pressure of the air loaded on the first sub-tank 6A, the second sub-tank 6B, and the third sub-tank 6C can be set to be constant regardless of the amount of fuel used and the remaining amount.

The control value of the air pressure may be set by directly using the amount of fuel used or the remaining amount in the first sub-tank 6A, the second sub-tank 6B and the third sub-tank 6C as a parameter, or the first sub-tank 6A, The difference or ratio between the maximum capacity and the remaining amount of fuel in the second sub tank 6B and the third sub tank 6C may be set as a parameter.

On the other hand, in the pressure adjustment system 22, it is possible to acquire the measured values of the pressures actually loaded in the first sub-tank 6A, the second sub-tank 6B, and the third sub-tank 6C from the respective pressure gauges 31A, 31B, 31C. it can.

The control value of the pressure of the air loaded on the first sub tank 6A, the second sub tank 6B and the third sub tank 6C is set, and the first sub tank 6A, the second sub tank 6B and the third sub tank 6C are set. When the measured value of the loaded pressure is acquired, the flow rate of the air to be supplied is set in the pressurized container 23 that houses the first sub tank 6A, the second sub tank 6B, and the third sub tank 6C, respectively. be able to. That is, the air supply amount can be set so that the difference between the control value of the pressure of the air to be loaded on each sub-tank 6 and the measured value of the pressure becomes small.

When the flow rate of the air to be supplied into the pressurizing container 23 that accommodates the first sub-tank 6A, the second sub-tank 6B, and the third sub-tank 6C is set, the control value of the opening degree of the supply air control valve 25 is set. Also, the control value of the opening degree of the exhaust air control valve 27 can be set respectively. Specifically, in the case of increasing the pressure in a certain pressurized container 23, the opening degree of the corresponding supply air control valve 25 increases while the opening degree of the discharge air control valve 27 decreases, Control signals for the supply air control valve 25 and the discharge air control valve 27 can be generated.

Each control signal generated in the pressure adjusting system 22 is output to the supply air control valve 25 and the discharge air control valve 27 as an electric signal or an air signal. That is, the opening degree of the supply air control valve 25 and the opening degree of the discharge air control valve 27 are controlled by the control signal from the pressure adjusting system 22. As a result, it is possible to bring the pressure in the pressure vessel 23 accommodating the first sub-tank 6A, the second sub-tank 6B, and the third sub-tank 6C close to the target value. For example, as the fuel consumption increases, the opening degree of the supply air control valve 25 is increased, while the opening degree of the discharge air control valve 27 is decreased, so that the pressure in each pressurizing container 23 is made constant or increased. You can

In the example shown in FIG. 3, the pressure in each pressurizing container 23 is the target of the feedback control or the feedforward control, but the fuel in the first sub-tank 6A, the second sub-tank 6B and the third sub-tank 6C is The pressure may be subject to feedback control or feedforward control. Further, instead of the amount of fuel used or the remaining amount of fuel in the first sub-tank 6A, the second sub-tank 6B and the third sub-tank 6C, in the first sub-tank 6A, the second sub-tank 6B and the third sub-tank 6C The pressure control value may be determined based on the fuel pressure. In that case, a pressure gauge for measuring the pressure of the fuel in the first sub tank 6A, the second sub tank 6B, and the third sub tank 6C is provided.

Thus, the pressure applied to the first sub-tank 6A, the second sub-tank 6B and the third sub-tank 6C, the pressure of the fuel in the first sub-tank 6A, the second sub-tank 6B and the third sub-tank 6C And, at least one of the remaining amount or the used amount of the fuel in the first sub-tank 6A, the second sub-tank 6B and the third sub-tank 6C is directly or indirectly measured, and based on the measured value, the pressure adjustment system 22 Thus, the control value of the pressure applied to the first sub tank 6A, the second sub tank 6B and the third sub tank 6C can be variably set.

According to the fuel supply system 1A in the second embodiment as described above, in addition to the same effects as the effects of the fuel supply system 1 in the first embodiment, the fuel tank 3 is loaded during the flight of the aircraft 2. The effect that the pressure distribution can be adjusted is obtained.

(Modification)
Also in the first embodiment, if a gas spring is used as the elastic body 12, the spring constant of the elastic body 12 can be controlled by adjusting the internal pressure of the gas spring. Therefore, also in the first embodiment, it is possible to control the pressure distribution similarly to the second embodiment. Even when a simple spring is used as the elastic body 12, if the elastic body 12 is connected to the tip of the expansion/contraction mechanism and the expansion/contraction amount of the expansion/contraction mechanism is controlled, the spring constant of the elastic body 12 is reduced. It becomes possible to variably control.

FIG. 4 shows that when a plurality of elastic bodies 12 apply pressure to the fuel tank 3 composed of the first sub-tank 6A, the second sub-tank 6B and the third sub-tank 6C, the spring constant of each elastic body 12 can be changed. It is a figure which shows the example at the time of making it controllable. In FIG. 4, constituent elements that are the same as or correspond to the constituent elements shown in FIG. 1 are assigned the same reference numerals and explanations thereof are omitted.

As shown in FIG. 4, each pressurizing mechanism 5</b>B included in the pressurizing system 4 of the fuel supply system 1</b>B can be configured by the elastic body 12 connected to the tip of the expansion/contraction mechanism 40. The elastic body 12 connected to the tip of the expansion mechanism 40 can pressurize the first sub tank 6A, the second sub tank 6B, and the third sub tank 6C, respectively.

For the extension/contraction mechanism 40, any extension/contraction mechanism utilizing a cylinder mechanism, a ball screw, a rack and pinion, or the like can be used. The expansion/contraction amount of each expansion/contraction mechanism 40 is configured to be controlled by the pressure adjustment system 22A. By changing the expansion/contraction amount of each expansion/contraction mechanism 40, the length of the elastic body 12 changes, so that the spring constant of the elastic body 12 can be variably controlled. Therefore, even when the first sub-tank 6A, the second sub-tank 6B and the third sub-tank 6C are pressurized with two or more different pressures, the elastic body 12 having the same spring constant can be used. ..

Specifically, the first sub-tank 6A and the third sub-tank 6C, which are separated from the center of gravity G of the aircraft 2, have a distal end of an expansion/contraction mechanism 40 in which the expansion/contraction amount is relatively long so that the spring constant is relatively large. The first elastic body 12A attached to the first sub-tank is crushed first, while the central second sub-tank 6B near the center of gravity G of the aircraft 2 has a relatively short expansion/contraction amount so that the spring constant becomes relatively small. The second elastic body 12B attached to the tip of the expansion/contraction mechanism 40 can be used for the final crushing. As a result, the amount of movement of the center of gravity of the fuel tank 3 and the amount of movement of the center of gravity G of the aircraft 2 due to fuel consumption can be reduced.

As described above, when the fuel tank 3 is pressurized by the pressurizing mechanism 5B having the structure shown in FIG. 4 or when the gas spring is used as the elastic body 12, the elastic force of the elastic body 12 is measured. By providing a necessary sensor such as a sensor, the pressure distribution applied to the fuel tank 3 during the flight of the aircraft 2 can be adjusted by the pressure adjusting system 22A.

That is, it is possible to perform feedback control or feedforward control targeting the elastic force of the elastic body 12 or the fuel pressure in the first sub tank 6A, the second sub tank 6B, and the third sub tank 6C. Further, the control value of the elastic force of the elastic body 12 or the control value of the expansion/contraction amount of the expansion/contraction mechanism 40 is set to the pressure, the remaining amount, or the use of the fuel in the first sub tank 6A, the second sub tank 6B, and the third sub tank 6C. It can be variably set based on the amount.

This makes it possible to perform control to increase the pressure applied to the first sub tank 6A, the second sub tank 6B, and the third sub tank 6C as the fuel is consumed. Alternatively, even if the fuel is consumed, it is possible to control the pressures applied to the first sub tank 6A, the second sub tank 6B, and the third sub tank 6C to be kept constant.

(Third Embodiment)
FIG. 5 is a configuration diagram of an aircraft including a fuel supply system according to a third embodiment of the present invention.

In the fuel supply system 1C according to the third embodiment shown in FIG. 5, the arrangement of the elastic body 12 for pressurizing the fuel tank 3 and the structure of the fuel tank 3 are different from those of the fuel supply system 1 according to the first embodiment. To do. Other configurations and operations of the fuel supply system 1C according to the third embodiment are substantially the same as those of the fuel supply system 1 according to the first embodiment, and therefore, the same or corresponding configurations are designated by the same reference numerals. The description is omitted.

The plurality of pressurizing mechanisms 5C included in the pressurizing system 4 of the fuel supply system 1C according to the third embodiment are each configured by the elastic body 12. However, each elastic body 12 is arranged such that the direction of the elastic force applied to the fuel tank 3 by the elastic body 12 is different from the vertical direction of the structure such as the fuselage of the aircraft 2 in which the fuel tank 3 is mounted. To be done. In other words, the direction of the elastic body 12 that applies the elastic force to the fuel tank 3 is not limited to the vertical direction of the structure of the aircraft 2, but can be any desired direction. Therefore, the direction of the elastic body 12 can be oriented toward the position of the center of gravity G of the body of the aircraft 2.

As a result, the amount of movement of the center of gravity G of the aircraft 2 due to the consumption of fuel in the fuel tank 3 can be reduced with a simple structure. In the example shown in FIG. 5, a generally cylindrical fuel tank 3 is mounted inside the body of a small unmanned aerial vehicle. Therefore, the structure of the pressurizing system 4 is such that the end surfaces on both sides of the fuel tank 3 are pressed by the two elastic bodies 12 from the left and right in a substantially horizontal direction. Therefore, the two elastic bodies 12 and the fuel tank 3 are arranged inside a cylindrical rigid casing 50 for restricting the expansion and contraction directions of the two elastic bodies 12 and for accommodating the generally cylindrical fuel tank 3. There is.

In the case of the example shown in FIG. 5, the fuel tank 3 does not necessarily have to be divided into a plurality of sub tanks 6. However, depending on the structure of the structure of the aircraft 2 in which the fuel tank 3 is mounted, the fuel tank 3 may be divided into a plurality of sub tanks 6, and each sub tank 6 may be pressurized by the elastic body 12 from a desired direction. ..

Regardless of whether or not the fuel tank 3 is divided into a plurality of sub-tanks 6, the pressurizing direction of the fuel tank 3 is arbitrary. For example, the fuel tank 3 may be pressurized obliquely downward. That is, it is possible to pressurize the fuel tank 3 in a direction different from the vertical direction of the structures such as the main wing and the fuselage of the aircraft 2 on which the fuel tank 3 is mounted. In this case, the fuel tank 3 is pressurized in a direction that is not perpendicular to the bottom surface of the casing that houses the fuel tank 3.

Of course, as shown in FIG. 4, the fuel tank 3 may be pressurized by the elastic body 12 connected to the tip of the expansion/contraction mechanism 40. Alternatively, the fuel tank 3 may be pressurized with air as in the second embodiment. Therefore, it is also possible to perform variable control of the pressure distribution applied to the fuel tank 3 during flight of the aircraft 2. When the fuel tank 3 is pressurized with air in a predetermined direction, the structure of the pressure container for housing the fuel tank 3 may be designed so that the air applies pressure to the fuel tank 3 in the predetermined direction.

In the fuel supply system 1C according to the third embodiment described above, the pressurizing directions of the fuel tank 3 by the plurality of pressurizing mechanisms 5C included in the pressurizing system 4 are set to the center of gravity G of the aircraft 2 due to fuel consumption. It is decided to reduce the movement amount. That is, the pressure distribution applied to the fuel tank 3 by the pressurization system 4 is a plurality of uniform pressure distributions applied from different directions. Therefore, according to the fuel supply system 1C of the third embodiment, it is possible to reduce the amount of movement of the center of gravity G of the aircraft 2 due to fuel consumption with a very simple configuration.

(Fourth Embodiment)
FIG. 6 is a configuration diagram of an aircraft including a fuel supply system according to a fourth embodiment of the present invention.

The fuel supply system 1D according to the fourth embodiment shown in FIG. 6 is different from the fuel supply system 1C according to the third embodiment in that the fuel tank 3 is pressurized by a single pressurizing mechanism 5D. .. Other configurations and operations of the fuel supply system 1D in the fourth embodiment are substantially the same as those of the fuel supply system 1C in the third embodiment, and thus the same or corresponding configurations are designated by the same reference numerals. The description is omitted.

When arbitrarily determining the pressurizing direction of the fuel tank 3 by the pressurizing system 4, as shown in FIG. 6, the single pressurizing mechanism 5D can pressurize the fuel tank 3 in one direction. For example, when the fuel tanks 3 are mounted inside the left and right main wings of the aircraft 2, the center of gravity of the aircraft 2 is inside the fuselage. In such a case, the fuel tank 3 mounted in each main wing can be pressurized toward the fuselage side by the single pressing mechanism 5D. As a result, the amount of movement of the center of gravity G of the aircraft 2 due to the consumption of fuel in the fuel tank 3 can be reduced with a simple structure.

In the example shown in FIG. 6, the simple elastic body 12 is used as the pressurizing mechanism 5D, but as shown in FIG. 4, the elastic body 12 connected to the tip of the expansion/contraction mechanism 40 or air is used for fuel. The tank 3 may be pressurized. Therefore, also in the fourth embodiment, it is possible to perform variable control of the pressure distribution applied to the fuel tank 3 during flight of the aircraft 2.

In the fuel supply system 1D according to the fourth embodiment as described above, the pressurizing direction of the fuel tank 3 by the single pressurizing mechanism 5D included in the pressurizing system 4 is set to be the center of gravity G of the aircraft 2 accompanying the fuel consumption. It is decided to reduce the movement amount of. That is, the pressure distribution applied to the fuel tank 3 by the pressurization system 4 is a uniform pressure distribution applied from one direction. Therefore, according to the fuel supply system 1D of the fourth embodiment, it is possible to reduce the amount of movement of the center of gravity G of the aircraft 2 that accompanies fuel consumption with a very simple configuration.

(Other embodiments)
Although the specific embodiments have been described above, the described embodiments are merely examples and do not limit the scope of the invention. The novel methods and apparatus described herein can be implemented in various other ways. In addition, various omissions, substitutions, and changes can be made in the method and apparatus described herein without departing from the spirit of the invention. The appended claims and their equivalents are intended to cover all such variations and modifications as fall within the scope and spirit of the invention.

For example, in each of the above-described embodiments, the case where the fuel tank 3 is pressurized by the elastic body 12 or air has been described, but the fuel tank 3 may be pressurized by hydraulic pressure. Particularly, in the case of an aircraft equipped with a hydraulic system that hydraulically drives structures such as wheels and wings, the fuel tank 3 can be pressurized by the hydraulic system.

Further, the features of the respective embodiments can be combined with each other.
Further, in each of the above-described embodiments, a case has been described as an example in which the amount of movement of the center of gravity of the body of the aircraft 2 due to fuel consumption is reduced. You may make it control to move.

1, 1A, 1B, 1C, 1D Fuel supply system 2 Aircraft 3 Fuel tank 4 Pressurization system 5, 5A, 5B, 5C, 5D Pressurization mechanism 6, 6A, 6B, 6C Sub-tank 7 Discharge port 8 Engine 9 Casing 10 Piping 11 Replenishment ports 12, 12A, 12B Elastic body 13 Pressing plate 20 Air extraction pipe 21 Air compressor 22, 22A Pressure adjusting system 23 Pressurizing container 24 Air supply port 25 Supply air control valve 26 Air discharge port 27 Discharge air control valve 30A , 30B, 30C Flowmeters 31A, 31B, 31C Pressure gauge 40 Expansion/contraction mechanism 50 Casing G Center of gravity

Claims (10)

A flexible fuel tank for an aircraft for storing fuel;
A pressurizing system for discharging the fuel from the fuel tank by pressurizing the fuel tank with a pressure distribution determined according to the position of the center of gravity of the aircraft on which the fuel tank is mounted;
Equipped with
The pressurizing system pressurizes a first portion of the fuel tank located at a position away from the position of the center of gravity of the aircraft with a first pressure, while the fuel supply system that will be configured to pressurize a low second pressure than the first pressure and the second portion of the close. The fuel supply system according to claim 1, wherein the pressurization system is configured to pressurize the fuel tank with a pressure distribution determined so that a movement amount of the position of the center of gravity due to consumption of the fuel is reduced. .. The fuel tank is arranged at a position overlapping the center of gravity,
The pressurized system, while pressurizing the first portion on both sides of the fuel tank remote from the center of gravity at the first pressure, the said second part of the center of the fuel tank closer to the center of gravity The fuel supply system according to claim 1 or 2 , wherein the fuel supply system is configured to pressurize at the second pressure lower than the first pressure. The fuel tank has a structure in which a plurality of sub-tanks are connected,
The fuel according to any one of claims 1 to 3 , wherein the pressurizing system is configured to pressurize the plurality of sub-tanks at a pressure determined for each of the sub-tanks by using a plurality of pressurizing mechanisms. Supply system. The fuel supply system according to claim 4 , wherein the fuel discharge port is provided only in one of the plurality of sub-tanks. The fuel supply system according to any one of claims 1 to 5 , wherein the pressurization system is configured to pressurize the fuel tank with air. The pressurized system is a fuel supply system according to any one of claims 1 to 5 configured to pressurize the fuel tank with the elastic body. The fuel supply system according to any one of claims 1 to 7 further comprising a pressure regulating system for adjusting the pressure distribution. In a fuel supply method for discharging the fuel from the fuel tank by pressurizing a flexible fuel tank for an aircraft for storing fuel,
By pressure of the fuel tank at the determined pressure distribution depending on the position of the center of gravity of the aircraft equipped with the fuel tank, a first portion of the fuel tank in a position away from the position of the center of gravity of the aircraft while pressurized with a first pressure, the fuel supply under pressure a second portion located closer than the first portion at a second pressure lower than the first pressure from the position of the center of gravity of the aircraft Method. An aircraft comprising the fuel supply system according to any one of claims 1 to 8 .

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