Aircraft fuel tank inerting system

Abstract

An aircraft fuel tank inerting system includes an air supply system for supplying inert gas to a main fuel tank and an auxiliary fuel tank. The aircraft fuel tank inerting system further includes: an inerting gas distribution pipe extending from the air supply system and branching into a first branch pipe and a second branch pipe, the first branch pipe connected to the main fuel tank and having a main fuel tank isolation valve disposed therein; and a second branch pipe connected to the auxiliary fuel tank and having an auxiliary fuel tank isolation valve disposed therein; and a first vent pipe connected between the main fuel tank and the auxiliary fuel tank and having a vent valve disposed therein, thereby enabling inerting gas to be replenished from the auxiliary fuel tank to the main fuel tank. This structure helps reduce the bleed air requirement of the inerting system and reduces the flammability of the auxiliary fuel tanks during ground operations.

Description

Technical Field

[0001] The present invention relates to the field of aircraft, in particular to the design of civil aircraft, and in particular to the design of an explosion-proof mechanism of an aircraft fuel tank. Background Art

[0002] On traditional aircraft, the aircraft's fuel tanks are typically installed on the center wing, and the wing fuel tanks are usually aluminum metal wing tanks. In addition, there is a new type of composite wing that includes multiple compartments. Both the center wing section with the aluminum metal wing fuel tank and the compartments of the new composite wing pose a risk of explosion. To prevent explosions, strict explosion-proof safety standards must be met during the aircraft design process. In addition, for some civil aircraft models, auxiliary fuel tanks are often installed in the cargo hold to increase the aircraft's fuel capacity to extend its range. Auxiliary fuel tanks are typical fuel tanks that are normally empty within the fuselage and are also subject to explosion-proof safety requirements.

[0003] Therefore, in the design of the aircraft, the design of the wing fuel tanks and auxiliary fuel tanks must meet certain explosion-proof safety standards, such as the flammability clauses of CCAR-25-R4 25.981 and Appendix M.

[0004] To meet flammability standards, a common measure is to install an inerting system on the aircraft's center wing section or on new composite wings. This system introduces inert gas into the aircraft's fuel tanks, reducing the oxygen content and, consequently, the risk of fuel explosion. For auxiliary fuel tanks, pressurization is typically used to increase the fuel's flammable temperature range, lowering its flammability and, consequently, reducing the risk of explosion.

[0005] Generally speaking, when designing a fuel tank inerting system, the primary consideration is the aircraft's descent phase. During this phase, the pressure differential drives a large influx of ambient air into the fuel tank, increasing the oxygen concentration within the tank. To address this increase in oxygen concentration and ensure that the oxygen concentration within the tank meets inerting requirements before and after landing, a large amount of inert gas must be injected into the tank during the aircraft's descent. This consumes a significant amount of engine bleed air to maintain the tank's post-flight inerting state.

[0006] Therefore, the inert gas flow rate during the descent phase determines the architecture and size of the inerting system. Because the inerting system's performance requirements during descent are far greater than those during other flight phases, significant redundancy exists in the inerting system's performance during these other phases. Generally, the inerting system's air source is engine bleed air. To optimize its use, a nitrogen-enriched dual-flow mode is employed on many aircraft models. This involves a high flow rate during descent and a low or medium flow rate during other phases. This flow control is accomplished through the installation of flow control valves and corresponding piping. This flow control structure increases the complexity of the inerting system.

[0007] For civil aircraft equipped with auxiliary fuel tanks, bleed air pressurization is generally used for fuel transfer, which can reduce the tank's flammability. However, when on the ground, the auxiliary fuel tanks are directly connected to the ambient atmosphere and are not pressurized. Furthermore, the air conditioning system's cooling effect on the cargo hold is relatively poor while on the ground. This leads to the risk of the auxiliary fuel tank's flammability exceeding the standard (exceeding the flammability limit of no more than 3% for auxiliary fuel tanks on the ground on hot days, as required by Appendix M).

[0008] In summary, the currently predominant inerting systems have the following problems: The inerting system is designed based on the demand for nitrogen-rich gas during the aircraft's descent phase, which results in redundant system performance during other phases; existing explosion-proof designs fail to consider the potential for excessive flammability of auxiliary fuel tanks on the ground; and, for civil aircraft equipped with auxiliary fuel tanks, the auxiliary fuel tanks utilize a bleed air pressurization system, which is independent of the main wing fuel tank inerting system and is not integrated, resulting in increased overall system complexity and high costs. Summary of the Invention

[0009] The present invention is designed to address the aforementioned problems existing in the prior art. It aims to provide an improved aircraft fuel tank inerting system that reduces system redundancy and improves overall system efficiency. Furthermore, the system is particularly suitable for civil aircraft equipped with auxiliary fuel tanks.

[0010] The aircraft fuel tank inerting system of the present invention includes an air supply system for supplying inert gas to a main fuel tank and an auxiliary fuel tank. The aircraft fuel tank inerting system further includes an inerting gas distribution pipe extending from the air supply system and branching into a first branch pipe and a second branch pipe. The first branch pipe is connected to the main fuel tank and includes a main fuel tank isolation valve. The second branch pipe is connected to the auxiliary fuel tank and includes an auxiliary fuel tank isolation valve. Furthermore, an air supply pipe is connected between the main fuel tank and the auxiliary fuel tank. The first air supply pipe includes a vent valve, thereby enabling inerting gas to be supplied from the auxiliary fuel tank to the main fuel tank.

[0011] This aircraft fuel tank inerting system utilizes auxiliary fuel tanks to store inert gas, leveraging their large capacity and high pressure resistance. During descent, the auxiliary tanks can be used to deliver inert gas to the main fuel tanks, eliminating the need for conventional high-flow modes. This reduces system performance requirements, lowers engine bleed air demand during descent, and reduces overall aircraft energy consumption. Furthermore, the inert gas in the auxiliary tanks can be used for fuel pressure boost transfer and, after landing, inert the auxiliary tanks, reducing their flammability on the ground.

[0012] Preferably, the auxiliary fuel tank is provided with: a cabin air bleed valve for supplying bleed air from the aircraft's cabin to the auxiliary fuel tank; and / or a pressure sensor for measuring the pressure in the auxiliary fuel tank, thereby monitoring the pressure difference between the auxiliary fuel tank and the cabin.

[0013] Preferably, the system further includes: a main fuel tank one-way valve, which is arranged on the first branch pipe; and / or an auxiliary fuel tank one-way valve, which is arranged on the second branch pipe.

[0014] The main fuel tank check valve and the auxiliary fuel tank check valve can be used to prevent the backflow of oil vapor or fuel from the main fuel tank and the auxiliary fuel tank.

[0015] Preferably, the aircraft fuel tank inerting system further comprises: a main fuel tank flow limiting hole, which is arranged on the first branch pipe and located upstream of the main fuel tank one-way valve; and / or an auxiliary fuel tank flow limiting hole, which is arranged on the second branch pipe and located upstream of the auxiliary fuel tank one-way valve.

[0016] The main fuel tank restriction holes and the auxiliary fuel tank restriction holes help reduce the inert gas flow rate and prevent excess gas from causing overpressure in the main fuel tank and the auxiliary fuel tank.

[0017] In a specific structure, the air supply system includes: an air source, which provides high-temperature bleed air; a bleed air regulating part, a high-temperature air pipeline is connected between the air source and the bleed air regulating part, and the high-temperature bleed air from the air source enters the bleed air regulating part through the high-temperature air pipeline; and an air separator, a normal-temperature air pipeline is connected between the bleed air regulating part and the air separator, and the regulated normal-temperature air from the bleed air regulating part enters the air separator through the normal-temperature air pipeline and is separated into oxygen-rich gas and nitrogen-rich gas, wherein the oxygen-rich gas is discharged through the oxygen-rich gas discharge pipe, and the nitrogen-rich gas serves as an inert gas and is input into the inert gas distribution pipe.

[0018] Preferably, the aircraft fuel tank inerting system further includes a controller capable of controlling the main fuel tank isolation valve, the auxiliary fuel tank isolation valve, the pressure sensor, and the vent valve.

[0019] Furthermore, a fuel delivery pipe is connected between the main fuel tank and the auxiliary fuel tank, and a fuel transfer valve is provided on the fuel delivery pipe for controlling the transfer of fuel from the auxiliary fuel tank to the main fuel tank.

[0020] The controller is configured to: during the cruise phase of the aircraft, open the main fuel tank isolation valve to input inert gas into the main fuel tank; and, when fuel transfer from the auxiliary fuel tank to the main fuel tank begins, open the auxiliary fuel tank check valve to pressurize the auxiliary fuel tank with inert gas.

[0021] Preferably, the controller is configured to alternately open the main fuel tank isolation valve and the auxiliary fuel tank isolation valve during the cruise phase, wherein when it is detected that the pressure differential between the auxiliary fuel tank and the passenger cabin reaches a second upper limit, the auxiliary fuel tank isolation valve is closed and the main fuel tank isolation valve is opened; and when it is detected that the pressure differential reaches a first lower limit, the auxiliary fuel tank isolation valve is opened and the main fuel tank isolation valve is closed.

[0022] Preferably, the controller is configured to open the vent valve during the descent phase of the aircraft, thereby replenishing the main fuel tank with inert gas from the auxiliary fuel tank.

[0023] Furthermore, the controller is further configured to close the vent valve when the pressure difference between the auxiliary fuel tank and the passenger cabin reaches a second lower limit value.

[0024] Preferably, the controller is configured to: during the descent phase of the aircraft, when the pressure difference between the auxiliary fuel tank and the passenger cabin reaches a first upper limit, open the vent valve to provide overpressure protection for the auxiliary fuel tank. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The specific embodiments of the present invention can be more clearly understood from the structures shown in the accompanying drawings, wherein:

[0026] Figure 1 Shown is a schematic structural diagram of the aircraft fuel tank inerting system of the present application.

[0027] (Explanation of Symbols)

[0028] 1 Air separator

[0029] 2 aircraft wings

[0030] 10 Main fuel tank

[0031] 11 First branch pipe

[0032] 12 Main fuel tank isolation valve

[0033] 13 Second ventilation pipe

[0034] 20 Auxiliary fuel tank

[0035] 21 Second branch pipe

[0036] 22 Auxiliary fuel tank isolation valve

[0037] 23 Pressure sensor

[0038] 31 Nitrogen-rich gas distribution pipe

[0039] 32 fuel delivery pipe

[0040] 33 Fuel transfer valve

[0041] 41 First ventilation pipe

[0042] 42 Vent valve

[0043] 50 Controller DETAILED DESCRIPTION

[0044] The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be understood that the drawings illustrate only preferred embodiments of the present invention and do not limit the scope of the present invention. Those skilled in the art may make various obvious modifications, variations, and equivalent substitutions to the present invention based on the embodiments shown in the drawings. Furthermore, the technical features of the different embodiments described below may be arbitrarily combined with each other, provided that no contradiction exists. All of these combinations fall within the scope of protection of the present invention.

[0045] Figure 1A schematic diagram of the aircraft fuel tank inerting system of the present application is shown. The aircraft fuel tank inerting system includes an air supply system. In the exemplary configuration shown in the figure, the air supply system specifically includes an air separator 1. The air separator 1 primarily separates air into two components: oxygen-rich gas with a high oxygen content and nitrogen-rich gas with a high nitrogen content. The resulting nitrogen-rich gas enters the aircraft's fuel tank system via a nitrogen-rich gas distribution pipe 31 extending from the air separator 1, as will be described in more detail below. The air entering the air separator 1 can, for example, be engine bleed air from the engine.

[0046] Preferably, the air supply system may further include other devices, such as a bleed air conditioning device, which can process relatively high-temperature air, such as engine bleed air, by, for example, cooling the gas, before feeding the gas into air separator 1 for separation. The oxygen-enriched gas generated in air separator 1 can be discharged or introduced into other applications requiring oxygen-enriched gas, while the nitrogen-enriched gas is used as an inerting gas and delivered via inerting gas distribution pipe 31 to the main fuel tank 10 and auxiliary fuel tank 20, described further below.

[0047] Next, the inert gas distribution pipe 34 is divided into two branch pipes, wherein the first branch pipe 11 is connected to the main fuel tank 10 , and the second branch pipe 21 is connected to the auxiliary fuel tank 20 .

[0048] A main fuel tank isolation valve 12 is provided on the first branch pipe 11 for controlling the supply of inert gas to the main fuel tank 10. Similarly, an auxiliary fuel tank isolation valve 22 is provided on the second branch pipe 21 for controlling the supply of inert gas to the auxiliary fuel tank 20.

[0049] Preferably, a one-way valve, a flow restriction orifice, and other components (not shown) may be further provided on the first branch pipe 11. The one-way valve prevents the backflow of gas or fuel within the main fuel tank 10 into upstream components such as the air separator 1. The flow restriction orifice may be located, for example, upstream of the one-way valve, near the outlet of the air separator 1, to prevent excessive gas from entering the main fuel tank 10 and causing overpressure.

[0050] Similarly, components such as a one-way valve and a flow restriction hole may also be provided in the second branch pipe 21 .

[0051] A first vent pipe 41 is connected between the main fuel tank 10 and the auxiliary fuel tank 20, and a vent valve 42 is provided on the first vent pipe 41. Specifically, the first vent pipe 41 is connected between the auxiliary fuel tank 20 and the main fuel tank 10 to balance the air pressure in the main fuel tank 10 and the auxiliary fuel tank 20 during refueling, and to replenish inert gas from the auxiliary fuel tank 20 to the main fuel tank 10.

[0052] As schematically shown in the figure, the main fuel tank 10 is arranged on the wing of the aircraft. In addition, a second vent pipe 13 is arranged on the wing 2 of the aircraft, and ambient air can flow into the main fuel tank 10 through the second vent pipe 13.

[0053] Preferably, a pressure sensor 26 is further installed on the auxiliary fuel tank 20 for measuring the pressure in the auxiliary fuel tank 20 .

[0054] In addition, preferably, in the present application, a cabin bleed air valve (not shown) may be provided on the auxiliary fuel tank 20 as a backup. Specifically, if the air supply system described above fails and stops working, the cabin bleed air valve may be opened to utilize cabin bleed air as a backup air source.

[0055] As shown in the figure, a fuel delivery pipe 32 is connected between the main fuel tank 10 and the auxiliary fuel tank 20 for transferring fuel between the main fuel tank 10 and the auxiliary fuel tank 20. A fuel transfer valve 33 is installed on the fuel delivery pipe 32.

[0056] Similar to the flow limiting holes mentioned above provided on the first branch pipe 11 and the second branch pipe 21, a fuel transfer flow limiting hole (not shown) is preferably also provided upstream of the fuel transfer valve 33 to protect the fuel transfer valve 33 from being damaged by excessive pressure drop.

[0057] The aircraft fuel tank inerting system of the present application further includes a controller 50 capable of controlling the operation of the aircraft fuel tank inerting system based on the aircraft's flight phase, parameters such as the pressure in the auxiliary fuel tank 20 measured by the pressure sensor 23, and the like. The controller 50 communicates with the main fuel tank isolation valve 12, the auxiliary fuel tank isolation valve 22, the pressure sensor 23, the fuel transfer valve 33, the vent valve 42, and the like via wired or wireless means to control the operation of the aircraft fuel tank inerting system.

[0058] In the aircraft fuel tank inerting system described above, the inerting system is integrated with the auxiliary fuel system. This leverages the advantages of the auxiliary fuel tank 20's large storage capacity and high pressure resistance. Before the aircraft's descent, the auxiliary fuel tank 20 is used to store inerting gas, such as nitrogen-enriched gas. After the aircraft enters its descent phase, the inerting gas stored in the auxiliary fuel tank 20 is used to replenish the main fuel tank 10. This reduces engine bleed air consumption during descent, alleviating the engine's operating load. This reduces both aircraft energy consumption and the overall weight of the inerting system.

[0059] On the other hand, the inert gas introduced into the auxiliary fuel tank 20 can also be used for the pressurization transmission function of the auxiliary fuel tank 20 , and also has an inerting effect on the auxiliary fuel tank 20 , thereby reducing the flammability of the auxiliary fuel tank 20 .

[0060] The following describes the operation of the aircraft fuel tank inerting system described above:

[0061] When the aircraft is on the ground, the refueling panel is opened to refuel the main fuel tank 10 and the auxiliary fuel tank 20. At this time, the vent valve 42 on the first vent pipe 41 opens, connecting the auxiliary fuel tank 20 with the main fuel tank 10 and maintaining the air pressure in the main and auxiliary fuel tanks 10, 20, consistent with the atmospheric pressure. At this point, the aircraft's fuel tank inerting system is in an inhibited state: the main and auxiliary fuel tank isolation valves 12 and 22 are closed, and the fuel transfer valve 33 is also closed.

[0062] During refueling, the pressure difference ΔP inside the auxiliary fuel tank 20 relative to the cabin can be monitored by pressure sensor 23. This pressure difference provides overpressure protection for the auxiliary fuel tank 20. For example, if ΔP exceeds a first upper limit, such as 10.5 psid, controller 50 will control vent valve 42 to open until the aircraft lands. Alternatively, other mechanical pressure relief valves can be installed as needed to enhance safety.

[0063] When the aircraft begins takeoff, the aircraft's fuel tank inerting system enters operation. At liftoff, vent valve 42 closes, and main fuel tank isolation valve 12 opens, allowing inert gas to be supplied from the air supply system to main fuel tank 10. During this phase, auxiliary fuel tank isolation valve 22 remains closed.

[0064] During the cruising phase of the aircraft, the controller 50 monitors the fuel level in the auxiliary fuel tank 20. When the fuel level in the auxiliary fuel tank 20 is lower than the set threshold value Q fuel When the fuel transfer valve 33 is opened, fuel transfer from the auxiliary fuel tank 20 to the main fuel tank 10 begins. Simultaneously with the start of fuel transfer, the auxiliary fuel tank isolation valve 22 opens, and inert gas begins to be supplied to the auxiliary fuel tank 20 to increase the pressure of the auxiliary fuel tank 20. Simultaneously, the main fuel tank isolation valve 12 can be closed, suspending the supply of inert gas to the main fuel tank 10.

[0065] In a specific application scenario, for example, at an altitude of 35,000 feet (ft), the oxygen concentration in the nitrogen-enriched gas supplied as the inerting gas is less than 4%. By supplying such inerting gas to the main fuel tank 10 and the auxiliary fuel tank 20, the flammability of the main fuel tank 10 and the auxiliary fuel tank 20 can be effectively reduced.

[0066] Next, during the fuel transfer and the introduction of inerting gas into the auxiliary fuel tank 20, the pressure sensor 23 monitors the pressure in the auxiliary fuel tank 20, and thus the pressure differential ΔP between the interior of the auxiliary fuel tank 20 and the interior of the passenger cabin. When this pressure differential reaches a second upper limit, for example, 10 psid, the auxiliary fuel tank isolation valve 22 is closed, halting pressurization of the auxiliary fuel tank 20. Simultaneously, the main fuel tank isolation valve 12 is opened, and inerting of the main fuel tank 10 continues.

[0067] While the main fuel tank 10 is being inerted, the pressure sensor 26 continuously monitors the pressure in the auxiliary fuel tank 20. As fuel from the auxiliary fuel tank 20 is transferred to the main fuel tank 10, the pressure in the auxiliary fuel tank 20 decreases. When the pressure in the auxiliary fuel tank 20 drops to a first lower limit, for example, 9 psid, the auxiliary fuel tank isolation valve 22 is reopened to resume pressurizing the auxiliary fuel tank 20. At this point, the main fuel tank isolation valve 12 can be closed to cease inerting the main fuel tank 10. When the pressure in the auxiliary fuel tank 20 reaches a second upper limit (for example, 10 psid), the auxiliary fuel tank isolation valve 22 is closed to cease pressurizing the auxiliary fuel tank 20. At this point, the main fuel tank isolation valve 12 can be opened to resume pressurizing the main fuel tank 10.

[0068] The above process repeats until the fuel in the auxiliary fuel tank 20 is depleted. At this point, the fuel transfer valve 33 is closed, halting fuel transfer. Furthermore, after the pressure in the auxiliary fuel tank isolation valve 22 reaches the upper limit, the auxiliary fuel tank isolation valve 22 is also closed, ceasing pressurization of the auxiliary fuel tank 20. Furthermore, the main fuel tank isolation valve 12 is opened, and inert pressurization of the main fuel tank 10 is initiated.

[0069] Preferably, during the pressurization and inerting process, if a failure occurs and it is difficult to supply inert gas from the air supply system, cabin bleed air can be introduced into the auxiliary fuel tank 20 through the cabin bleed air valve as a backup air source.

[0070] When the aircraft enters its descent phase, vent valve 42 immediately opens, allowing inert gas stored in auxiliary fuel tank 20 to flow into main fuel tank 10. Auxiliary fuel tank 20 preferably gradually depressurizes until the pressure differential ΔP between the auxiliary fuel tank 20 and the passenger cabin reaches a second lower limit, which is less than the first lower limit, for example, 0.1 psid. After the pressure differential ΔP reaches the second lower limit, vent valve 42 closes.

[0071] Furthermore, during descent, the auxiliary fuel tank 20 continues to depressurize the main fuel tank 10 until after landing. Design estimates indicate that this depressurization will take 30 minutes, covering the entire descent. During this process, fresh air from the outside environment is replenished into the main fuel tank 10 via the second vent pipe 13 and mixed with the inerting gas (e.g., nitrogen-enriched gas) in the main fuel tank 10. By controlling the inerting gas flow rate, the oxygen concentration in the main fuel tank 10 after the flight is maintained below the limit of 12%. This ensures that the main fuel tank 10 remains inerted until the next flight.

[0072] After the aircraft lands, the main fuel tank isolation valve 12 closes, and the aircraft's fuel tank inerting system ceases operation. As can be seen from the above description, during the descent phase, the auxiliary fuel tank 20 remains depressurized, preventing the entry of outside air into the auxiliary fuel tank 20. Therefore, the auxiliary fuel tank 20 remains in an inerted state from landing until the next flight, reducing its flammability on the ground.

[0073] Experiments have shown that the aircraft fuel tank inerting system of the present application and its corresponding operating mode allow the high-flow mode used in the prior art to be eliminated, leaving only the low-flow mode. This still ensures that the oxygen concentration in the main fuel tank 10 and the auxiliary fuel tank 20 is below the explosion-proof standard, i.e., below 12%, after the flight. Specific examples are as follows:

[0074] The volume of the gas phase space in the aircraft's main fuel tank is 17m 3 The auxiliary fuel tank gas phase volume is 17 m 3 , and the 35,000 ft cruise stage as an example. Generally speaking, the nitrogen-enriched gas flow rate in the low-flow mode cruise stage is 4g / s (the corresponding high-flow rate is 4 times the low-flow rate), and the oxygen concentration of the nitrogen-enriched gas is below 4%.

[0075] The experiment showed that the cumulative pressurization time during the aircraft's cruise phase was 123 minutes, the engine fuel consumption rate was 35 kg / min, the auxiliary fuel tanks supported the engine fuel supply for more than 360 minutes, and the aircraft's cruise flight time exceeded 720 minutes. This indicates that pressurizing the auxiliary fuel tanks only accounts for a small portion of the cruise phase and has no significant impact on the inerting system's ability to inert the main fuel tanks.

[0076] Furthermore, at 35,000 feet, the cabin pressure differential relative to ambient was 8.17 psid, and the auxiliary fuel tank pressurization differential relative to the cabin was 10 psid. Based on the Monte Carlo descent rate, the descent phase took 20.4 minutes, with a ground ambient pressure of 14.7 psia and a barometric pressure of 3.459 psia at 35,000 feet. The average nitrogen-enriched gas flow rate in the main fuel tank during descent was 5 g / s, with an oxygen concentration of 6%.

[0077] Based on the above parameters, under the single-tank mixing model, using the aircraft fuel tank inerting system of this application, the average oxygen concentration in the main fuel tank at the end of the flight is calculated as follows:

[0078] The cumulative mass of oxygen passing through the gas phase space of the central wing during the descent phase (unit: kg) is A=4.1466;

[0079] The cumulative air mass (unit: kg) passing through the central wing gas phase space during the descent phase is B=35.5653;

[0080] Therefore, the oxygen concentration C=A / B=11.66%<12%.

[0081] As can be seen, using the aircraft fuel tank inerting system of the present application, when not in high-flow mode, the oxygen concentration in the main fuel tank is less than 12%, meeting flammability standards. Furthermore, as mentioned above, since the auxiliary fuel tanks are constantly depressurized during descent, no outside air enters, thus resolving the issue of excessive flammability in the auxiliary fuel tanks during ground operations.

Claims

1. An aircraft fuel tank inerting system, comprising an air supply system for supplying inerting gas to a main fuel tank and an auxiliary fuel tank, characterized in that: The aircraft fuel tank inerting system further comprises: an inert gas distribution pipe extending from the gas supply system and branching into a first branch pipe and a second branch pipe, the first branch pipe being connected to the main fuel tank and having a main fuel tank isolation valve disposed therein, and the second branch pipe being connected to the auxiliary fuel tank and having an auxiliary fuel tank isolation valve disposed therein; and a first vent pipe connected between the main fuel tank and the auxiliary fuel tank, and provided with a vent valve for replenishing inert gas from the auxiliary fuel tank to the main fuel tank; The auxiliary fuel tank is provided with a pressure sensor, which can measure the pressure in the auxiliary fuel tank, thereby monitoring the pressure difference between the auxiliary fuel tank and the passenger cabin of the aircraft; The aircraft fuel tank inerting system further includes a controller capable of controlling the main fuel tank isolation valve, the auxiliary fuel tank isolation valve, the pressure sensor, and the vent valve, and the controller is configured to: alternately open the main fuel tank isolation valve and the auxiliary fuel tank isolation valve during a cruising phase of the aircraft, wherein when it is detected that the pressure differential between the auxiliary fuel tank and the passenger cabin reaches a second upper limit, the auxiliary fuel tank isolation valve is closed and the main fuel tank isolation valve is opened; and when it is detected that the pressure differential reaches a first lower limit, the auxiliary fuel tank isolation valve is opened and the main fuel tank isolation valve is closed.

2. The aircraft fuel tank inerting system according to claim 1, wherein: Also includes: a main fuel tank one-way valve, the main fuel tank one-way valve being arranged on the first branch pipe; and / or An auxiliary fuel tank one-way valve is provided on the second branch pipe.

3. The aircraft fuel tank inerting system according to claim 1, wherein: The gas supply system comprises: An air separator is provided for separating air into oxygen-rich gas and nitrogen-rich gas, wherein the oxygen-rich gas is discharged and the nitrogen-rich gas serves as the inert gas and is input into the inert gas distribution pipe.

4. The aircraft fuel tank inerting system according to claim 1, wherein: A fuel delivery pipe is connected between the main fuel tank and the auxiliary fuel tank. A fuel transfer valve is provided on the fuel delivery pipe for controlling the transfer of fuel from the auxiliary fuel tank to the main fuel tank.

5. The aircraft fuel tank inerting system according to claim 4, wherein: The controller is configured to open the vent valve to provide overpressure protection for the auxiliary fuel tank when detecting that the pressure difference between the auxiliary fuel tank and the passenger cabin exceeds a first upper limit.

6. The aircraft fuel tank inerting system according to claim 4, wherein: The controller is configured to: during the cruise phase, open the main fuel tank isolation valve to input the inert gas into the main fuel tank; and, when fuel transfer from the auxiliary fuel tank to the main fuel tank is initiated, open the auxiliary fuel tank check valve to pressurize the auxiliary fuel tank with the inert gas.

7. The aircraft fuel tank inerting system according to claim 4, wherein: The controller is configured to open the vent valve during a descent phase of the aircraft, thereby replenishing inert gas from the auxiliary fuel tank to the main fuel tank.

8. The aircraft fuel tank inerting system according to claim 7, wherein: The controller is configured to close the vent valve when the pressure difference between the auxiliary fuel tank and the passenger cabin reaches a second lower limit.

9. The aircraft fuel tank inerting system according to claim 4, wherein: The aircraft further comprises a second vent pipe connected to the main fuel tank, wherein during the descent phase of the aircraft, air from the external environment can enter the main fuel tank via the second vent pipe.

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