Aircraft auxiliary fuel tank fuel transfer and pressurization and combustion reduction system and aircraft

Abstract

The invention relates to a fuel transfer and pressurization and combustion reduction system for an auxiliary fuel tank of an airplane and the airplane. The fuel transfer, pressurization and combustion reduction system for the auxiliary fuel tank of the airplane comprises an auxiliary fuel tank unit, an auxiliary fuel tank bleed air isolation valve, a heat exchanger, an auxiliary fuel tank bleed air temperature sensor, an auxiliary fuel tank pressure sensor, a first anti-backflow one-way valve and a second anti-backflow one-way valve. In the flight stage, a passenger cabin bleed air is normally open and serves as a transmission power source to enter the auxiliary fuel tank unit through the first anti-backflow one-way valve; wherein in the ground stage, pressurized bleed air passes through an auxiliary fuel tank bleed air isolating valve, is cooled by the heat exchanger and then enters the auxiliary fuel tank unit, an auxiliary fuel tank bleed air temperature sensor and a second anti-backflow one-way valve are arranged between the heat exchanger and the auxiliary fuel tank unit, and the pressure of the auxiliary fuel tank unit is increased by 0.5-1.0 PSI relative to the external atmospheric pressure.

Description

Technical Field

[0001] This invention relates to the field of aircraft design, and more particularly to aircraft fuel tank systems. Background Technology

[0002] Business-class or extended-range commercial aircraft are equipped with auxiliary fuel tanks (AFTs) to meet specific customer requirements for long range and extended flight time. On most mainstream commercial aircraft, AFTs are primarily installed in the cargo hold and are considered internal fuselage fuel tanks. According to AFT classification, AFTs must meet the flammability requirements of CCAR25-R4 Annex M25.1. The fleet average flammability exposure time for each fuel tank, as determined in Appendix N of this Part, shall not exceed 3% of the flammability exposure assessment time (FEET) as defined in Appendix N of this Part. The fleet average flammability exposure time for each fuel tank, as defined in Appendix N of this Part, shall not exceed 3% of the warm weather conditions in the ground or takeoff / climb phases of the FEET.

[0003] The flammability of AFT (Air-to-Fuel) is affected by the thermal environment of the cargo hold and the pressurization level of the fuel tank. Based on practical experience, it is believed that if no targeted flammability reduction design is adopted and the cooling effect of the cabin air conditioning returning to the cargo hold is relied upon, there is a risk of exceeding the flammability limit during the warm weather ground / climb phase of AFT.

[0004] For energy conservation and explosion protection purposes, the auxiliary fuel tank system (AFTS) of mainstream aircraft models is currently pressurized. The characteristic of pressurized AFTS is that it uses the cabin or other pressure sources to pressurize the auxiliary fuel tank (AFT) to achieve fuel transfer.

[0005] A typical supercharged AFTS for civil aircraft contains multiple AFT units, of which the main AFT unit directly supplies fuel to the base fuel tank, while the others are auxiliary AFT units. The fuel collection tank section of the base fuel tank directly supplies fuel to the engine.

[0006] The specific working process of the pressurized AFTS: During flight, the transfer subsystem uses the bleed air pressurization subsystem to introduce cabin pressurized gas or other processed high-pressure bleed air as the transfer power source into the auxiliary fuel tank, and uses the pressure difference between the auxiliary fuel tank and the basic fuel tank to transfer the fuel in the auxiliary fuel tank to the basic fuel tank.

[0007] Currently, AFTS (Air Fuel Tank System) flammability reduction mainly involves integrated design with the inerting system. In addition to using NEA (nitrogen-rich gas) as a transfer pressure source, after the transfer is completed, nitrogen-rich gas is stored in the auxiliary fuel tank. This fully utilizes the large space and high pressure resistance of the auxiliary fuel tank to store excess NEA. During the descent phase, the nitrogen-rich gas stored in the auxiliary fuel tank is controlled to enter the base fuel tank. This can both replenish the inerting of the base fuel tank and maintain the inerting state of the auxiliary fuel tank after the aircraft lands, reducing the flammability of the auxiliary fuel tank during the ground and climb phases of the next flight.

[0008] Typical aircraft air conditioning systems are designed only for the cockpit and passenger cabin, lacking cooling features for the cargo hold. For AFTs located within the cargo hold, in warm weather conditions, the cargo hold cannot be guaranteed to be cooled, causing their flammability to fail to meet Clause 25.981 during warm weather ground and climb phases. Current technical solutions employ inerting for flammability reduction during both ground and climb phases. To meet the airworthiness requirements for AFT installations, significant modifications to the inerting system design are necessary, increasing development costs. Summary of the Invention

[0009] One objective of this invention is to provide an aircraft auxiliary fuel tank fuel transfer and pressurization system that enables the auxiliary fuel tank to meet relevant flammability requirements during warm weather ground / climb phases without requiring significant changes to the inerting system design, thereby reducing development costs.

[0010] The above-mentioned objectives of the present invention are achieved by an aircraft auxiliary fuel tank fuel transfer and pressurization and combustion reduction system, which includes: an auxiliary fuel tank unit, an auxiliary fuel tank bleed air isolation valve, a heat exchanger, an auxiliary fuel tank bleed air temperature sensor, an auxiliary fuel tank pressure sensor, a first anti-backflow check valve, and a second anti-backflow check valve. The auxiliary fuel tank bleed air temperature sensor is located upstream of the boost bleed air direction of the auxiliary fuel tank unit to sense the temperature of the boost bleed air in the auxiliary fuel tank, and the auxiliary fuel tank pressure sensor is located in the auxiliary fuel tank unit to sense the pressure inside the auxiliary fuel tank unit. During flight, the cabin bleed air is always open and serves as a power transfer source, entering the auxiliary fuel tank unit via the first anti-backflow check valve. During the ground phase, the boosted bleed air passes through the auxiliary fuel tank bleed air isolation valve, is cooled by the heat exchanger, and then enters the auxiliary fuel tank unit. The auxiliary fuel tank bleed air temperature sensor and the second anti-backflow check valve are installed between the heat exchanger and the auxiliary fuel tank unit. The auxiliary fuel tank unit is pressurized by 0.5~1.0 PSI relative to the external atmospheric pressure.

[0011] According to the above technical solution, the aircraft auxiliary fuel tank fuel transfer and pressurization and combustion reduction system of the present invention can achieve the following beneficial technical effects: it can make the flammability of the auxiliary fuel tank meet the relevant flammability requirements during the warm weather ground / climb phase, and does not require significant changes to the inerting system design, thus reducing development costs.

[0012] Preferably, the pressurized bleed air is obtained by compressing outside air using an air compressor.

[0013] Preferably, the booster bleed air is engine bleed air, which does not require compression by an air compressor.

[0014] Preferably, the auxiliary fuel tank unit includes a first auxiliary fuel tank unit and a second auxiliary fuel tank unit, wherein the first auxiliary fuel tank unit and the second auxiliary fuel tank unit are connected by an air pipe and a fuel pipe.

[0015] Preferably, the aircraft auxiliary fuel tank fuel transfer and pressurization and combustion reduction system further includes a first flow restrictor and a second flow restrictor. The pressurized bleed air passes through the first flow restrictor before entering the first auxiliary fuel tank unit, and the pressurized bleed air passes through the second flow restrictor before entering the second auxiliary fuel tank unit.

[0016] Preferably, the aircraft auxiliary fuel tank fuel transfer and pressurization system further includes a third flow restrictor, through which the cabin bleed air passes before entering the auxiliary fuel tank unit.

[0017] Preferably, the aircraft auxiliary fuel tank fuel transfer and pressurization system further includes a pressure relief valve, which is located between the auxiliary fuel tank unit and the vent tank. During flight, when the pressure difference between the auxiliary fuel tank unit and the external atmospheric pressure exceeds 10.0 PSI, the pressure relief valve opens, and the gas in the auxiliary fuel tank unit is discharged into the external atmosphere through the vent tank.

[0018] Preferably, the engine bleed air is cooled by the inlet isolation valve and the heat exchanger and then divided into two paths. One path enters the auxiliary fuel tank unit through the auxiliary fuel tank bleed air isolation valve, the auxiliary fuel tank bleed air temperature sensor and the second anti-backflow check valve; the other path enters the base fuel tank through the inerting system.

[0019] Preferably, the inerting system includes a base fuel tank temperature isolation valve, an air separator inlet pressure sensor, an air separator inlet temperature sensor, an air separator, a flow limiting device, and a base fuel tank anti-backflow check valve. The other path enters the air separator via the base fuel tank temperature isolation valve, the air separator inlet pressure sensor, and the air separator inlet temperature sensor. Nitrogen-rich gas enters the base fuel tank for inerting via the flow limiting device and the base fuel tank anti-backflow check valve, while oxygen-rich gas is discharged into the atmosphere.

[0020] The above-mentioned objectives of the present invention are also achieved by an aircraft comprising an aircraft auxiliary fuel tank fuel transfer and pressurization and fuel reduction system as described in any of the above aspects.

[0021] According to the above technical solution, the aircraft of the present invention can achieve the following beneficial technical effects: it can ensure that the flammability of the auxiliary fuel tank meets the relevant flammability requirements during the warm weather ground / climb phase, and does not require significant changes to the inerting system design, thereby reducing development costs. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the architecture of the aircraft auxiliary fuel tank fuel transfer and pressurization and combustion reduction system according to the first embodiment of the present invention.

[0023] Figure 2 This is a schematic diagram of the architecture of the aircraft auxiliary fuel tank fuel transfer and pressurization and combustion reduction system according to the second embodiment of the present invention.

[0024] Figure 3 This is a schematic diagram of the architecture of the aircraft auxiliary fuel tank fuel transfer and pressurization and combustion reduction system according to the third embodiment of the present invention.

[0025] List of reference numerals

[0026] 1: Auxiliary fuel tank bleed air isolation valve; 2: Air compressor; 3: Heat exchanger; 4: Auxiliary fuel tank bleed air temperature sensor; 5: Second anti-backflow check valve; 6: Second flow-limiting orifice; 7: First flow-limiting orifice; 8: Auxiliary fuel tank pressure sensor; 9: Third flow-limiting orifice; 10: First anti-backflow check valve; 11: Pressure relief valve; 21: Imported isolation valve; 23: Heat exchanger outlet temperature sensor; 24: Basic fuel tank temperature isolation valve; 25: Air separator inlet pressure sensor; 26: Air separator inlet temperature sensor; 27: Air separator; 28: Current limiting device; 29: Basic fuel tank anti-backflow check valve. Detailed Implementation

[0027] The following describes specific embodiments of the present invention. It should be noted that, in order to provide a concise description, this specification cannot exhaustively describe all features of the actual embodiments. It should be understood that, in the actual implementation of any embodiment, just as in any engineering or design project, various specific decisions are often made to achieve the developer's specific goals and to meet system-related or business-related constraints, and this can change from one embodiment to another. Furthermore, it is understood that although the efforts made in this development process may be complex and lengthy, for those skilled in the art related to the content disclosed in this invention, some design, manufacturing, or production modifications based on the technical content disclosed herein are merely conventional technical means and should not be construed as insufficient content of this disclosure.

[0028] Unless otherwise defined, the technical or scientific terms used in the claims and description shall have the ordinary meaning understood by one of ordinary skill in the art to which this invention pertains. The terms "first," "second," and similar terms used in the patent application description and claims of this invention do not indicate any order, quantity, or importance, but are merely used to distinguish different components. The terms "an" or "a" and similar terms do not indicate a quantity limitation, but rather indicate the presence of at least one. The terms "comprising" or "including" and similar terms mean that the element or object preceding "comprising" or "including" encompasses the element or object listed following "comprising" or "including" and its equivalents, and do not exclude other elements or objects. The terms "connected" or "linked" and similar terms are not limited to physical or mechanical connections, nor are they limited to direct or indirect connections.

[0029] In the following description, in order to clearly demonstrate the structure and working method of the present invention, a number of directional terms will be used. However, terms such as "front", "back", "left", "right", "outer", "inner", "outward", "inward", "up", and "down" should be understood as convenient terms and not as limiting terms.

[0030] Figure 1This is a schematic diagram of the architecture of the aircraft auxiliary fuel tank fuel transfer and pressurization and combustion reduction system according to the first embodiment of the present invention. Figure 2 This is a schematic diagram of the architecture of the aircraft auxiliary fuel tank fuel transfer and pressurization and combustion reduction system according to the second embodiment of the present invention. Figure 3 This is a schematic diagram of the architecture of the aircraft auxiliary fuel tank fuel transfer and pressurization and combustion reduction system according to the third embodiment of the present invention.

[0031] According to a general concept of the present invention, such as Figures 1 to 3 As shown, an auxiliary fuel tank fuel transfer and pressurization and combustion reduction system for aircraft is provided. The auxiliary fuel tank fuel transfer and pressurization and combustion reduction system includes: an auxiliary fuel tank unit, an auxiliary fuel tank bleed air isolation valve 1, a heat exchanger 3, an auxiliary fuel tank bleed air temperature sensor 4, an auxiliary fuel tank pressure sensor 8, a first anti-backflow check valve 10, and a second anti-backflow check valve 5. Among them, the auxiliary fuel tank bleed air temperature sensor 4 is located upstream of the boost bleed air direction of the auxiliary fuel tank unit to sense the temperature of the boost bleed air of the auxiliary fuel tank, and the auxiliary fuel tank pressure sensor 8 is located in the auxiliary fuel tank unit to sense the pressure inside the auxiliary fuel tank unit. During the flight phase, the cabin bleed air is always open and serves as a power transfer source, entering the auxiliary fuel tank unit via the first anti-backflow check valve 10. During the ground phase, the boosted bleed air passes through the auxiliary fuel tank bleed air isolation valve 1, is cooled by the heat exchanger 3, and then enters the auxiliary fuel tank unit. An auxiliary fuel tank bleed air temperature sensor 4 and a second anti-backflow check valve 5 are installed between the heat exchanger 3 and the auxiliary fuel tank unit. The auxiliary fuel tank unit is pressurized by 0.5~1.0 PSI (pounds per square inch) relative to the external atmospheric pressure.

[0032] According to the above technical solution, the aircraft auxiliary fuel tank fuel transfer and pressurization and combustion reduction system of the present invention can achieve the following beneficial technical effects: it can make the flammability of the auxiliary fuel tank meet the relevant flammability requirements during the warm weather ground / climb phase, and does not require significant changes to the inerting system design, thus reducing development costs.

[0033] Preferably, such as Figure 1 As shown, the booster bleed air is obtained by compressing outside air through the air compressor 2.

[0034] Preferably, such as Figures 2 to 3 As shown, booster bleed air is engine bleed air, which does not require compression by an air compressor.

[0035] Preferably, such as Figures 1 to 3 As shown, the auxiliary fuel tank unit includes a first auxiliary fuel tank unit and a second auxiliary fuel tank unit, which are connected by an air pipe and a fuel pipe.

[0036] Preferably, such as Figures 1 to 3 As shown, the aircraft auxiliary fuel tank fuel transfer and pressurization and combustion reduction system also includes a first flow restrictor 7 and a second flow restrictor 6. The pressurized bleed air passes through the first flow restrictor 7 before entering the first auxiliary fuel tank unit, and the pressurized bleed air passes through the second flow restrictor 6 before entering the second auxiliary fuel tank unit.

[0037] Preferably, such as Figures 1 to 3 As shown, the aircraft auxiliary fuel tank fuel transfer and pressurization system also includes a third flow restrictor 9, through which cabin bleed air passes before entering the auxiliary fuel tank unit.

[0038] Preferably, such as Figures 1 to 3 As shown, the aircraft auxiliary fuel tank fuel transfer and pressurization system also includes a pressure relief valve 11. The pressure relief valve 11 is located between the auxiliary fuel tank unit and the vent tank. During flight, when the pressure difference between the auxiliary fuel tank unit and the outside atmospheric pressure exceeds 10.0 PSI, the pressure relief valve 11 opens, and the gas in the auxiliary fuel tank unit is discharged into the outside atmosphere through the vent tank.

[0039] (First embodiment)

[0040] Figure 1 This is a schematic diagram of the architecture of the aircraft auxiliary fuel tank fuel transfer and pressurization / burner reduction system according to the first embodiment of the present invention. The auxiliary fuel tank system architecture proposed in the first embodiment of the present invention only allows normal venting during the refueling phase to achieve pressure balance between the auxiliary fuel tank and the external environment; during other phases, it is closed-loop venting. During flight, the cabin bleed air is always open, and the pressure inside the auxiliary fuel tank is close to the cabin pressure, with a pressure difference of approximately 8.0 PSI between the auxiliary fuel tank and the outside atmosphere. The base fuel tank is open-loop venting, and its pressure remains consistent with atmospheric pressure. When the pressure of the auxiliary fuel tank relative to the atmosphere exceeds 10.0 PSI, the pressure relief valve 11 opens, and the gas inside the fuel tank is discharged into the atmosphere through the vent tank. During the ground phase, the auxiliary fuel tank is pressurized by 0.5~1.0 PSI (relative to the outside atmospheric pressure) through the auxiliary pressurization subsystem, which enables the auxiliary fuel tank to reduce combustion during warm-weather ground conditions and the climb phase.

[0041] Preferably, such as Figure 1 As shown, during flight, the cabin bleed air is always open and serves as a power transfer source, entering the first auxiliary fuel tank unit via the third flow restrictor 9 and the first backflow prevention check valve 10. The first and second auxiliary fuel tank units are connected by an air pipe and an oil pipe. The second auxiliary fuel tank unit is equipped with an auxiliary fuel tank pressure sensor 8. When the pressure of the auxiliary fuel tank relative to the atmosphere exceeds 10.0 PSI, the pressure relief valve 11 opens, and the gas in the fuel tank is discharged into the atmosphere through the vent tank. When cabin bleed air is insufficient, outside air during the ground phase is pressurized by 0.5~1.0 PSI (relative to outside atmospheric pressure) through auxiliary fuel tank bleed air isolation valve 1 and air compressor 2 to obtain high temperature and high pressure gas. After being cooled by heat exchanger 3, it enters the auxiliary fuel tank. Auxiliary fuel tank bleed air temperature sensor 4 and second anti-backflow check valve 5 are installed between heat exchanger 3 and the second auxiliary fuel tank unit. After being cooled by heat exchanger 3, the bleed air enters the first auxiliary fuel tank unit through the first flow restriction orifice 7 and enters the second auxiliary fuel tank unit through the second flow restriction orifice 6.

[0042] (Second Embodiment)

[0043] Figure 2 This is a schematic diagram of the architecture of the aircraft auxiliary fuel tank fuel transfer and pressurization / burner reduction system according to the second embodiment of the present invention. The auxiliary fuel tank system architecture proposed in the second embodiment of the present invention only allows normal venting during the refueling phase to achieve pressure balance between the auxiliary fuel tank and the external environment; during other phases, it is closed-loop venting. During flight, the cabin bleed air is always open, and the pressure inside the auxiliary fuel tank is close to the cabin pressure, with a pressure difference of approximately 8.0 PSI between the auxiliary fuel tank and the outside atmosphere. The base fuel tank is open-loop venting, and its pressure remains consistent with atmospheric pressure. When the pressure of the auxiliary fuel tank relative to the atmosphere exceeds 10.0 PSI, the pressure relief valve 11 opens, and the gas inside the fuel tank is discharged into the atmosphere through the vent tank. Engine bleed air serves as an auxiliary power source, and its temperature is regulated via a heat exchanger. During the ground phase, the auxiliary fuel tank is pressurized by 0.5~1.0 PSI (relative to ambient atmospheric pressure). By changing the fuel-air ratio in the tank, explosions are suppressed, ensuring that the flammability meets standards during warm-weather ground conditions and the climb phase in AFT. The auxiliary fuel tank has a built-in pressure sensor that can control the tank pressurization in a closed loop.

[0044] Preferably, such as Figure 2 As shown, during flight, the cabin bleed air is always open and serves as a power transfer source, entering the first auxiliary fuel tank unit via the third flow restrictor 9 and the first backflow prevention check valve 10. The first and second auxiliary fuel tank units are connected by an air pipe and an oil pipe. The second auxiliary fuel tank unit is equipped with an auxiliary fuel tank pressure sensor 8. When the pressure of the auxiliary fuel tank relative to the atmosphere exceeds 10.0 PSI, the pressure relief valve 11 opens, and the gas in the tank is discharged into the atmosphere through the vent tank. When cabin bleed air is insufficient, the engine bleed air in the ground phase is cooled by the auxiliary fuel tank bleed air isolation valve 1 and heat exchanger 3 before entering the auxiliary fuel tank. An auxiliary fuel tank bleed air temperature sensor 4 and a second anti-backflow check valve 5 are installed between the heat exchanger 3 and the second auxiliary fuel tank unit. The bleed air cooled by the heat exchanger 3 enters the first auxiliary fuel tank unit through the first flow restriction orifice 7 and enters the second auxiliary fuel tank unit through the second flow restriction orifice 6.

[0045] (Third embodiment)

[0046] Figure 3 This is a schematic diagram of the architecture of the aircraft auxiliary fuel tank fuel transfer and pressurization / burner reduction system according to the third embodiment of the present invention. The auxiliary fuel tank system architecture proposed in the third embodiment of the present invention only allows normal venting during the refueling phase to achieve pressure balance between the auxiliary fuel tank and the external environment; during other phases, it is closed-loop venting. During flight, the cabin bleed air is always open, and the pressure inside the auxiliary fuel tank is close to the cabin pressure, with a pressure difference of approximately 8.0 PSI between the auxiliary fuel tank and the outside atmosphere. The base fuel tank is open-loop venting, and its pressure remains consistent with atmospheric pressure. When the pressure of the auxiliary fuel tank relative to the atmosphere exceeds 10.0 PSI, the pressure relief valve 11 opens, and the gas inside the fuel tank is discharged into the atmosphere through the vent tank. Engine bleed air serves as an auxiliary power source, sharing the inerting system's bleed air regulation subsystem (including, for example, an inlet isolation valve and a heat exchanger), thus avoiding the need for a separate heat exchanger. After being cooled by the inlet isolation valve and the heat exchanger (preferably also equipped with a heat exchanger outlet temperature sensor), the engine bleed air is divided into two paths. One path enters the auxiliary fuel tank via the auxiliary fuel tank bleed air isolation valve, the auxiliary fuel tank bleed air temperature sensor, and the second anti-backflow check valve, pressurizing the auxiliary fuel tank by 0.5~1.0 PSI (relative to ambient atmospheric pressure) during the ground phase, suppressing explosions by altering the fuel-air ratio within the tank. The other path enters the air separator via the base fuel tank temperature isolation valve, the air separator inlet pressure sensor, and the air separator inlet temperature sensor. Nitrogen-rich gas enters the base fuel tank for inerting via a flow limiting device and the base fuel tank anti-backflow check valve, while oxygen-rich gas is discharged into the atmosphere.

[0047] Preferably, such as Figure 3 As shown, during flight, the cabin bleed air is always open and serves as a power transfer source, entering the first auxiliary fuel tank unit via the third flow restrictor 9 and the first backflow prevention check valve 10. The first and second auxiliary fuel tank units are connected by an air pipe and an oil pipe. The second auxiliary fuel tank unit is equipped with an auxiliary fuel tank pressure sensor 8. When the pressure of the auxiliary fuel tank relative to the atmosphere exceeds 10.0 PSI, the pressure relief valve 11 opens, and the gas in the tank is discharged into the atmosphere through the vent tank. The engine bleed air is cooled by the inlet isolation valve 21 and the heat exchanger 3 (preferably also equipped with a heat exchanger outlet temperature sensor 23) and then split into two paths. One path enters the auxiliary fuel tank through the auxiliary fuel tank bleed air isolation valve 1, the auxiliary fuel tank bleed air temperature sensor 4, and the second anti-backflow check valve 5. It then enters the first auxiliary fuel tank unit through the first flow limiting orifice 7 and the second auxiliary fuel tank unit through the second flow limiting orifice 6, and is used for ground pressurization and combustion reduction during the ground stage. The other path enters the air separator 27 through the base fuel tank temperature isolation valve 24, the air separator inlet pressure sensor 25, and the air separator inlet temperature sensor 26. The nitrogen-rich gas enters the base fuel tank for inerting through the flow limiting device 28 and the base fuel tank anti-backflow check valve 29, while the oxygen-rich gas is discharged into the atmosphere.

[0048] This invention presents three auxiliary fuel tank system architectures with pressurization and flame reduction functions, particularly those that reduce the flammability of the auxiliary fuel tank on the ground and during climb. In the three designs, cabin bleed air pressurization and closed-loop ventilation are used to reduce the flammability of the fuel tank during air-to-ground (AFT) operation. The auxiliary pressurization subsystem (including, for example, an auxiliary fuel tank bleed air isolation valve, heat exchanger, auxiliary fuel tank bleed air temperature sensor, and a second backflow prevention check valve) is used to reduce the flammability of the fuel tank on the ground during AFT operation, and can also support AFT fuel transfer when cabin bleed air fails or cabin pressure differential is low. Compared to other measures, ground pressurization and flame reduction has the advantage of directly using existing fuel pressurization and transfer equipment without introducing new equipment. Only minor modifications to existing system products are needed to meet design requirements, resulting in better engineering practicality.

[0049] According to another general concept of the present invention, the aircraft includes an auxiliary fuel tank fuel transfer and pressurization / flammability reduction system as described in any of the above aspects. Based on the above technical solutions, the aircraft of the present invention can achieve the following beneficial technical effects: it enables the auxiliary fuel tank to meet relevant flammability requirements during warm weather / climb phases without requiring significant changes to the inerting system design, thus reducing development costs.

[0050] The specific embodiments of the present invention have been described above. However, those skilled in the art will understand that the above specific embodiments do not constitute a limitation on the present invention. Those skilled in the art can make various modifications based on the above disclosure without exceeding the scope of the present invention.

Claims

1. A fuel transfer, pressurization, and fuel reduction system for an aircraft auxiliary fuel tank, the system comprising: Auxiliary fuel tank unit, auxiliary fuel tank bleed air isolation valve, heat exchanger, auxiliary fuel tank bleed air temperature sensor, auxiliary fuel tank pressure sensor, first anti-backflow check valve, second anti-backflow check valve; The auxiliary fuel tank bleed air temperature sensor is located upstream of the boost bleed air direction of the auxiliary fuel tank unit to sense the temperature of the boost bleed air in the auxiliary fuel tank, and the auxiliary fuel tank pressure sensor is located in the auxiliary fuel tank unit to sense the pressure inside the auxiliary fuel tank unit. During flight, the cabin bleed air is always open and serves as a power transfer source, entering the auxiliary fuel tank unit via the first anti-backflow check valve. During the ground phase, the boosted bleed air passes through the auxiliary fuel tank bleed air isolation valve, is cooled by the heat exchanger, and then enters the auxiliary fuel tank unit. The auxiliary fuel tank bleed air temperature sensor and the second anti-backflow check valve are installed between the heat exchanger and the auxiliary fuel tank unit. The auxiliary fuel tank unit is pressurized by 0.5~1.0 PSI relative to the external atmospheric pressure.

2. The aircraft auxiliary fuel tank fuel transfer and pressurization system as described in claim 1, characterized in that, The pressurized bleed air is obtained by compressing outside air using an air compressor.

3. The aircraft auxiliary fuel tank fuel transfer and pressurization system as described in claim 1, characterized in that, The booster bleed air is engine bleed air, which does not require compression by an air compressor.

4. The aircraft auxiliary fuel tank fuel transfer and pressurization system as described in claim 1, characterized in that, The auxiliary fuel tank unit includes a first auxiliary fuel tank unit and a second auxiliary fuel tank unit, which are connected by an air pipe and a fuel pipe.

5. The aircraft auxiliary fuel tank fuel transfer and pressurization system as described in claim 4, characterized in that, The aircraft auxiliary fuel tank fuel transfer and pressurization system further includes a first flow restrictor and a second flow restrictor. The pressurized bleed air passes through the first flow restrictor before entering the first auxiliary fuel tank unit, and the pressurized bleed air passes through the second flow restrictor before entering the second auxiliary fuel tank unit.

6. The aircraft auxiliary fuel tank fuel transfer and pressurization system as described in claim 1, characterized in that, The aircraft auxiliary fuel tank fuel transfer and pressurization system also includes a third flow restrictor, through which the cabin bleed air passes before entering the auxiliary fuel tank unit.

7. The aircraft auxiliary fuel tank fuel transfer and pressurization system as described in claim 1, characterized in that, The aircraft auxiliary fuel tank fuel transfer and pressurization system also includes a pressure relief valve, which is located between the auxiliary fuel tank unit and the vent tank. During flight, when the pressure difference between the auxiliary fuel tank unit and the outside atmospheric pressure exceeds 10.0 PSI, the pressure relief valve opens, and the gas in the auxiliary fuel tank unit is discharged into the outside atmosphere through the vent tank.

8. The aircraft auxiliary fuel tank fuel transfer and pressurization system as described in claim 3, characterized in that, The engine bleed air is cooled by the inlet isolation valve and heat exchanger and then split into two paths. One path enters the auxiliary fuel tank unit through the auxiliary fuel tank bleed air isolation valve, the auxiliary fuel tank bleed air temperature sensor and the second anti-backflow check valve; the other path enters the base fuel tank through the inerting system.

9. The aircraft auxiliary fuel tank fuel transfer and pressurization system as described in claim 8, characterized in that, The inerting system includes a base fuel tank temperature isolation valve, an air separator inlet pressure sensor, an air separator inlet temperature sensor, an air separator, a flow limiting device, and a base fuel tank anti-backflow check valve. The other path enters the air separator through the base fuel tank temperature isolation valve, the air separator inlet pressure sensor, and the air separator inlet temperature sensor. Nitrogen-rich gas enters the base fuel tank for inerting through the flow limiting device and the base fuel tank anti-backflow check valve, while oxygen-rich gas is discharged into the atmosphere.

10. An aircraft comprising an auxiliary fuel tank fuel transfer and pressurization system as described in any one of claims 1-9.

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