Aircraft composite fuel tank inerting system

Abstract

The aircraft composite fuel tank inerting system includes: a gas source distribution pipeline; a central wing inerting branch connected to the central wing fuel tank; and an outer wing inerting branch connected to the outer wing fuel tank. The central wing inerting branch is equipped with a first inert gas generator and a multi-flow switching valve located downstream of the first inert gas generator, which can switch between a first flow mode and a second flow mode. The flow rate of the inert gas provided in the first flow mode is less than that in the second flow mode. The outer wing inerting branch is equipped with a second inert gas generator and a first flow restrictor located downstream of the second inert gas generator. The first flow restrictor enables a single flow mode, injecting inert gas into the central wing fuel tank in such a way that the initial oxygen concentration in the central wing fuel tank during the descent phase is below a first upper limit threshold, and injecting inert gas into the outer wing fuel tank in such a way that the oxygen concentration in the outer wing fuel tank during the cruise phase is below a second upper limit threshold that is higher than the first upper limit threshold.

Description

Technical Field

[0001] This invention relates to an inerting system for aircraft composite fuel tanks, belonging to the field of fuel tank explosion-proof technology. Background Technology

[0002] For weight reduction purposes, the fuel tank structure of the new generation of civil aircraft is mostly made of composite materials. The fuel tanks of this type of aircraft are not traditional unheated aluminum wing fuel tanks. In order to comply with the FAR / CCAR25-R4 25.981 fuel tank explosion protection requirements, both the internal and external fuel tanks of this type of aircraft need to be equipped with inerting systems for combustion reduction design, that is, full fuel tank inerting is required. The larger the target fuel tank volume, the greater the flow rate of inert gas required by the inerting system. The larger the inerting system, the more bleed air is required, and the greater the weight. Especially in wide-body aircraft, the need to reduce the weight of the inerting system, reduce the system bleed air, and improve the overall efficiency of the aircraft is becoming increasingly urgent.

[0003] A wide-body aircraft inerting system is known, in which all fuel tanks share a nitrogen-rich gas (NEA) distribution pipeline trunk line. The flow rate of all fuel tanks is controlled by a flow mode switching valve set in the trunk line. The outer wing and center wing adopt a high flow rate mode during the descent phase and a low flow rate mode during other phases. The NEA demand in the high flow rate mode determines the number of air separation modules (ASM). The existing inerting system architecture design results in an excessively high NEA demand, an increased number of core equipment ASMs, an increased engine bleed air, a large system weight, and reduced aircraft efficiency. Summary of the Invention

[0004] The present invention was made in view of the above-mentioned problems, and its purpose is to provide an aircraft composite fuel tank inerting system that can reduce the weight of the inerting system, reduce the system bleed air, and improve the overall efficiency of the aircraft.

[0005] To achieve the above objectives, the present invention provides an aircraft composite fuel tank inerting system, comprising: a gas source distribution pipeline; a center wing inerting branch, which branches off from the gas source distribution pipeline and is connected to the center wing fuel tank; and an outer wing inerting branch, which branches off from the gas source distribution pipeline and is connected to the outer wing fuel tank. The center wing inerting branch is equipped with a first inert gas generator and a multi-flow switching valve. The first inert gas generator receives gas to be processed from a gas source and generates inert gas. The multi-flow switching valve is located downstream of the first inert gas generator and can switch between a first flow mode and a second flow mode. The flow rate of the inert gas provided in the first flow mode is less than that of the gas source distribution pipeline. The inert gas flow rate provided in the second flow mode, the outer wing inerting branch is provided with a second inert gas generator and a first flow limiter. The second inert gas generator receives the gas to be processed from the gas source and generates inert gas. The first flow limiter is located downstream of the second inert gas generator. The single flow mode is realized through the first flow limiter. The aircraft composite fuel tank inerting system is configured to inject inert gas into the center wing fuel tank in such a way that the initial oxygen concentration in the center wing fuel tank during the descent phase is below a first upper limit threshold, and to inject inert gas into the outer wing fuel tank in such a way that the oxygen concentration in the outer wing fuel tank during the cruise phase is below a second upper limit threshold that is higher than the first upper limit threshold.

[0006] According to the aircraft composite fuel tank inerting system of the present invention, a differentiated inert gas generation and inert gas distribution subsystem design is adopted for different fuel tanks of aircraft models that require full fuel tank inerting. The central wing inerting branch leading to the central wing fuel tank is equipped with a first inert gas generator and a multi-flow switching valve, and the outer wing inerting branch leading to the outer wing fuel tank is equipped with a second inert gas generator and a first flow limiting device, forming a multi-branch inerting system design scheme.

[0007] According to the CCAR / FAR 25.981 requirements for flammability analysis of composite fuel tanks, the outer wing fuel tanks do not require inerting during climb and descent. Inert gas (e.g., NEA) injection into the outer wing fuel tanks can be stopped during climb and descent. The existing inerting system architecture does not support differentiated inerting functions for the outer wing and center wing, resulting in a large inert gas demand, increased engine bleed air, large system weight, and reduced aircraft efficiency.

[0008] This invention designs differentiated inert gas generation and distribution subsystems for the center wing and outer wing. The center wing fuel tank adopts a multi-flow mode, while the outer wing fuel tank adopts a single-flow mode, achieving different oxygen concentration control targets. This reduces the amount of inert gas required by the outer wing fuel tank, reduces the overall weight of the inerting system, reduces system bleed air, and improves aircraft economy.

[0009] Furthermore, in the aircraft composite fuel tank inerting system of the present invention, the gas source distribution pipeline may also include an air preparation subsystem capable of adjusting the pressure and temperature of the gas source. Based on the above structure, the pressure and temperature of the inlet bleed air from the first and second inert gas generators can be adjusted, which helps to improve the inerting performance.

[0010] Furthermore, in the aircraft composite fuel tank inerting system of the present invention, a pressure regulating and temperature regulating device may be provided upstream of the first inert gas generator in the center wing inerting branch. This device can regulate the pressure and temperature of the gas to be treated from the gas source. Similarly, a temperature regulating device may be provided upstream of the second inert gas generator in the outer wing inerting branch. This device can regulate the temperature of the gas to be treated from the gas source. Based on the above structure, to address the differentiated inerting requirements of the center wing fuel tank and the outer wing fuel tank, the center wing inerting branch adopts a pressure regulating design. The pressure regulating unit operates, for example, during the descent phase, increasing the inlet bleed air pressure of the first inert gas generator to improve inerting performance. The outer wing inerting branch, however, does not require a pressure regulating design.

[0011] For example, the outer wing inerting branch branches off at a position downstream of the first flow restrictor into a left outer wing inerting branch connected to the left outer wing fuel tank and a right outer wing inerting branch connected to the right outer wing fuel tank.

[0012] Furthermore, in the aircraft composite fuel tank inerting system of the present invention, preferably, two or more anti-backflow check valves connected in series are provided in the center wing inerting branch downstream of the multi-flow switching valve. This further reliably prevents fuel backflow into upstream equipment. Preferably, an anti-backflow check valve is provided in the outer wing inerting branch downstream of the first flow restrictor and upstream of the bifurcation points of the left and right outer wing inerting branches, and anti-cross-flow check valves are provided in the left and right outer wing inerting branches respectively. This reliably prevents fuel backflow into upstream equipment and prevents cross-flow between the left and right outer wing fuel tanks.

[0013] Furthermore, in the aircraft composite fuel tank inerting system of the present invention, the central wing inerting branch may be connected to multiple nozzles at its downstream end, and at least a portion of the left outer wing inerting branch and the right outer wing inerting branch may be located outside the central wing fuel tank. This reduces the amount of equipment installed inside the fuel tank.

[0014] Furthermore, in the aircraft composite fuel tank inerting system of the present invention, it may also include an ejector inlet pipe, wherein the central wing inerting branch is connected to an ejector pump at its downstream end, so that the gas in the central wing fuel tank is mixed with the inert gas entering the central wing fuel tank through the ejector inlet pipe before being injected into the central wing fuel tank. This improves the inerting uniformity within the central wing fuel tank.

[0015] Furthermore, the aircraft composite fuel tank inerting system of the present invention may also include a controller capable of controlling the operation of the multi-flow switching valve.

[0016] Furthermore, in the aircraft composite fuel tank inerting system of the present invention, for example, the first upper limit threshold is 4% or less, and the second upper limit threshold is 14.5% or less.

[0017] Furthermore, in the aircraft composite fuel tank inerting system of the present invention, the inert gas may be a nitrogen-rich gas, and the first inert gas generator and the second inert gas generator may each use a hollow fiber membrane air separation module. When the first and second inert gas generators use hollow fiber membrane air separation modules, the number of air separation modules can be reduced, or the diameter of the air separation module (the hollow fiber membrane) can be decreased, reducing the weight of the air separation module and the bleed air volume. The first flow restrictor may be a flow restricting orifice. Attached Figure Description

[0018] Figure 1 A schematic structural diagram of an aircraft composite fuel tank inerting system according to an embodiment of the present invention is shown.

[0019] Figure 2 A schematic structural diagram of an aircraft composite fuel tank inerting system according to another embodiment of the present invention is shown.

[0020] Figure 3 A schematic structural diagram of an aircraft composite fuel tank inerting system according to another embodiment of the present invention is shown.

[0021] Symbol Explanation

[0022] 1. Air Preparation Subsystem

[0023] 1a Voltage and temperature regulating device

[0024] 1b Temperature control device

[0025] 2 First Inert Gas Generator

[0026] 3 Second Inert Gas Generator

[0027] 4 First current limiting component

[0028] 5. Multi-flow switching valve

[0029] 6a, 6b, 6c anti-backflow check valves

[0030] 7a, 7b Current limiting components

[0031] 8a, 8b inert gas nozzles

[0032] 9. Left outer wing fuel tank

[0033] 10 Right outer wing fuel tank

[0034] 11 center wing fuel tanks

[0035] 12 Left Vent Fuel Tank

[0036] 13 Right-side vent fuel tank

[0037] 15a Central Wing Fuel Tank Vent Pipe

[0038] 15b Left Outer Wing Fuel Tank Vent Pipe

[0039] 15c right outer wing fuel tank vent pipe

[0040] 16 ejector pump

[0041] 17. Jet Inlet Pipe

[0042] 18a and 18b anti-cross-flow check valves

[0043] 19 Central Wing Inert Gas Distribution Branch

[0044] L1 gas source distribution pipeline

[0045] L2 Central Wing Inerting Branch

[0046] L3 outer wing inerting branch

[0047] L4 Left Outer Wing Inertization Branch

[0048] L5 right outer wing inerting branch Detailed Implementation

[0049] Hereinafter, with reference to the accompanying drawings, the technical solutions of embodiments and modifications of the present invention will be described. Furthermore, the scope of the present invention is not limited to the following embodiments and modifications, and can be arbitrarily modified within the scope of the technical concept of the present invention. In addition, in the following drawings, for ease of understanding of each structure, the actual construction may sometimes differ from the scale, quantity, etc., in each construction.

[0050] <First Implementation>

[0051] Figure 1 A schematic structural diagram of an aircraft composite fuel tank inerting system according to a first embodiment of the present invention is shown. The aircraft composite fuel tank inerting system includes an air source distribution line L1, a center wing inerting branch line L2, and an outer wing inerting branch line L3.

[0052] Air supply distribution line L1 supplies air. Air supply distribution line L1 may be equipped with an air preparation subsystem 1. Air preparation subsystem 1 can regulate the pressure and temperature of the air source. Air preparation subsystem 1 can employ any existing pressure and temperature regulation methods for air preparation; the specific processing will not be elaborated here. Alternatively, the air source may be, for example, engine bleed air from an engine. Air preparation subsystem 1 can process the relatively high-temperature air from engine bleed air, such as by cooling or pressurizing the gas, and then input the gas into a subsequent inert gas generator for gas separation.

[0053] The central wing inerting branch L2 and the outer wing inerting branch L3 branch off from the gas source distribution line L1. That is, one end of the central wing inerting branch L2 and one end of the outer wing inerting branch L3 are connected to the gas source distribution line L1 in a manner that allows gas to flow. Figure 1 In the example, the central wing inerting branch L2 and the outer wing inerting branch L3 branch off from the same position in the gas source distribution pipeline L1.

[0054] The other end (downstream end) of the central wing inerting branch L2 is connected to the central wing fuel tank 11 (the oil-free space). The central wing inerting branch L2 is equipped with a first inert gas generator 2 and a multi-flow switching valve 5. The first inert gas generator 2 receives the gas to be treated from the gas source and generates nitrogen-enriched air (NEA) as the inert gas. In this embodiment, the first inert gas generator 2 is a hollow fiber membrane air separation unit (ASM). Multiple first inert gas generators 2 can be connected in parallel. Figure 1 In the example, two first inert gas generators 2 are set in parallel. Alternatively, only one first inert gas generator 2 can be set.

[0055] The multi-flow switching valve 5 is located downstream of the first inert gas generator 2 and can be switched between a first flow mode (low flow mode) and a second flow mode (high flow mode). The flow rate of the inert gas (NEA in this embodiment) provided in the first flow mode is less than the flow rate of the inert gas (NEA in this embodiment) provided in the second flow mode. In this embodiment, the multi-flow switching valve 5 is configured as a dual-flow switching valve.

[0056] Preferably, a one-way valve for preventing fuel backflow, i.e., an anti-backflow one-way valve, is provided downstream of the multi-flow switching valve 5 in the central wing inerting branch L2. More preferably, two or more valves connected in series are provided. Figure 1 In the example, two anti-backflow check valves, 6b and 6c, are used, which can further improve the reliability of preventing fuel backflow and avoid single-point failure.

[0057] Furthermore, the aircraft composite fuel tank inerting system of this embodiment may include an ejector inlet duct 17. The ejector inlet duct 17 is provided, for example, in the center wing fuel tank 11. The center wing inerting branch L2 may be connected to the ejector pump 16 at its downstream end, so that the gas in the center wing fuel tank 11 is mixed with the inert gas (NEA in this embodiment) entering the center wing fuel tank 11 via the ejector inlet duct 17 and the center wing inerting branch L2 before being filled into the center wing fuel tank.

[0058] The other end (downstream end) of the outer wing inerting branch L3 is connected to the outer wing fuel tank (oil-free space). The outer wing inerting branch L3 is equipped with a second inert gas generator 3 and a first flow restrictor 4. The second inert gas generator 3 receives the gas to be treated from the gas source and generates inert gas (NEA in this embodiment). In this embodiment, the second inert gas generator 3 employs a hollow fiber membrane air separator module (ASM).

[0059] The first flow restrictor 4 is located downstream of the second inert gas generator 3. In the outer wing inerting branch L3, a single-flow mode is achieved through the first flow restrictor 4. That is, the first flow restrictor 4 is installed on the outer wing inerting branch L3, and a single-flow mode is used throughout the entire flight. The first flow restrictor helps reduce the inert gas (NEA) flow rate, preventing excessive gas from causing fuel tank overpressure, etc. The first flow restrictor is, for example, a flow-limiting device with a fixed orifice, such as a flow-limiting orifice (single-flow mechanical flow-limiting orifice).

[0060] Furthermore, the outer wing inerting branch L3 branches off downstream of the first flow restrictor 4, branching into a left outer wing inerting branch L4 connected to the left outer wing fuel tank 9 and a right outer wing inerting branch L5 connected to the right outer wing fuel tank 10. That is, one end of the left outer wing inerting branch L4 and one end of the right outer wing inerting branch L5 are connected to the outer wing inerting branch L3 in a manner that allows gas flow. The outer wing inerting branch L3 is connected to the left outer wing fuel tank 9 (the oil-free space) via the left outer wing inerting branch L4, and to the right outer wing fuel tank 10 (the oil-free space) via the right outer wing inerting branch L5. Figure 1 In the example, the left outer wing inerting branch L4 and the right outer wing inerting branch L5 branch from the same position of the outer wing inerting branch L3.

[0061] In addition, an inert gas nozzle 8a can be connected to the other end of the inerting branch L4 on the left outer wing. An inert gas nozzle 8b can be connected to the other end of the inerting branch L5 on the right outer wing.

[0062] Preferably, a backflow prevention check valve 6a is provided in the outer wing inerting branch L3, downstream of the first flow restrictor 4 and upstream of the bifurcation points of the left outer wing inerting branch L4 and the right outer wing inerting branch L5. Preferably, a check valve 18a for preventing cross-contamination of oil between the left and right outer wing oil tanks is provided in the left outer wing inerting branch L4. Preferably, a cross-contamination prevention check valve 18b is provided in the right outer wing inerting branch L5.

[0063] In addition, a flow-limiting component 7a (e.g., a flow-limiting orifice) may be provided in the left outer wing inerting branch L4, and a flow-limiting component 7b (e.g., a flow-limiting orifice) may be provided in the right outer wing inerting branch L5. The flow-limiting component 7a may be located downstream of the anti-cross-flow check valve 18a or upstream of the anti-cross-flow check valve 18a. The flow-limiting component 7b may be located downstream of the anti-cross-flow check valve 18b or upstream of the anti-cross-flow check valve 18b.

[0064] In addition, a controller (not shown) may be included, which can communicate with the multi-flow switching valve 5, etc., via wired or wireless means to control the operation of the aircraft composite fuel tank inerting system. For example, the controller can control the operation of the multi-flow switching valve 5 according to the flight phase of the aircraft.

[0065] For example, through flammability analysis of composite fuel tanks on wide-body aircraft, it was identified that the flammability requirements for outer wing composite fuel tanks are lower than those for center wing fuel tanks. They do not need to meet the requirement of flammability below 3% during the ground / climb phase in warm weather (temperatures above 26.7°C). The flammability reduction system design for outer wing fuel tanks can differ from that of center wing fuel tanks. The cruise phase contributes the most to the flammability of the outer wing's foundation, accounting for approximately 90% of the total flammability time. Therefore, it is only necessary to ensure that the outer wing fuel tanks are inerted during the cruise phase, with no requirements for other phases, to guarantee that the flammability of the outer wing fuel tanks is below 3%. This means that it is not necessary to impose the same restrictions on the oxygen concentration of the outer wing fuel tanks during the descent phase as the center wing fuel tanks.

[0066] In view of the above, the inventors have achieved global optimization by designing differentiated air separation and inert gas distribution subsystems for the center wing and outer wings, thereby improving the overall economic efficiency of the aircraft. This reduces the amount of inert gas required by the outer wing fuel tank, lowers the requirements for the system (e.g., reducing the number or size of ASMs, reducing engine bleed air), reduces the overall weight of the inerting system, and improves the aircraft's economy.

[0067] The aircraft composite fuel tank inerting system of the present invention is configured to inject inert gas into the center wing fuel tank 11 such that the initial oxygen concentration in the center wing fuel tank 11 during the descent phase is below a first upper limit threshold, and to inject inert gas into the outer wing fuel tanks 9 and 10 such that the oxygen concentration in the outer wing fuel tanks 9 and 10 during the cruise phase is below a second upper limit threshold, wherein the second upper limit threshold is higher than the first upper limit threshold. Here, "oxygen concentration" refers to the oxygen concentration in the fuel tank (also called "fuel tank") in the fuel-free space. For example, the first upper limit threshold is 4% or less, and the second upper limit threshold is 14.5% or less.

[0068] Furthermore, a venting system connecting the aircraft fuel tanks to the outside can be implemented via the left vent fuel tank 12 and the right vent fuel tank 13 located near the wingtip. A center wing fuel tank vent line 15a can be provided on the wing, connecting the center wing fuel tank 11 to the right vent fuel tank 13. Additionally, a left outer wing fuel tank vent line 15b can be provided, connecting the left outer wing fuel tank 9 to the left vent fuel tank 12; and a right outer wing fuel tank vent line 15c can be provided, connecting the right outer wing fuel tank 10 to the right vent fuel tank 13. Multiple ( Figure 1 In the example, the two left outer wing fuel tank vent pipes 15b are connected to different positions of the left outer wing fuel tank 9, and multiple pipes can also be connected. Figure 1 In the example, the two right outer wing fuel tank vent pipes 15c are respectively connected to different positions of the right outer wing fuel tank 10.

[0069] In addition, pressure sensors, temperature sensors (not shown) can be installed in the central wing fuel tank 11, outer wing fuel tanks 9 and 10, and other components such as shut-off valves can be installed in several pipelines / branches.

[0070] The operation process of the aircraft composite fuel tank inerting system described above will be described below.

[0071] The induced gas from the gas source system enters the first inert gas generator 2 and the second inert gas generator 3 through the air preparation subsystem 1;

[0072] The inert gas (nitrogen-rich gas in this embodiment) generated by the first inert gas generator 2 enters the central wing fuel tank 11 through the multi-flow switching valve 5 and two anti-backflow check valves 6b and 6c.

[0073] The inert gas pipeline (downstream of the central wing inerting branch L2) entering the central wing fuel tank 11 is connected to the ejector pump 16, so that the gas in the central wing fuel tank 11 is mixed with the inert gas (in this embodiment, nitrogen-rich gas) entering the central wing fuel tank through the ejector inlet pipeline 17 before being filled into the central wing fuel tank 11, thereby improving the inerting uniformity in the central wing fuel tank 11.

[0074] The inert gas (nitrogen-rich gas in this embodiment) generated by the second inert gas generator 3 enters the oil tank through a single-flow mechanical flow-limiting orifice (first flow-limiting element 4) and an anti-backflow check valve 6a, and then splits into two streams: the left side (refer to...) Figure 1 The fuel enters the left outer wing fuel tank 9 through the anti-crossing check valve 18a, the distribution flow restrictor 7a, and the inert gas nozzle 8a; the right side (refer to...) Figure 1 The fuel enters the right outer wing fuel tank 10 through the anti-crossing check valve 18b, the distribution flow restrictor 7b, and the inert gas nozzle 8b.

[0075] During the climb and cruise phases, the multi-flow switching valve 5 is controlled in the first flow mode (low flow mode). During the descent phase, the multi-flow switching valve 5 switches to the second flow mode (high flow mode). When the aircraft descends to a certain altitude (e.g., 4000ft), the multi-flow switching valve 5 switches back to the low flow mode until the aircraft lands, at which point the system shuts down.

[0076] In the aircraft composite fuel tank inerting system of the present invention, there are two branches for generating and distributing inert gas. Inert gas (nitrogen-rich gas, NEA) is injected into the fuel tank. One branch is injected into the center wing fuel tank 11, and the other branch is injected into the outer wing fuel tanks 9 and 10. The two branches correspond to different inert gas generators.

[0077] The inert gas distribution branch corresponding to the center wing fuel tank 11 (i.e., the center wing inerting branch L2 leading to the center wing fuel tank 11) adopts a multi-flow mode, which is achieved through a dual-flow switching valve. For example, during the descent phase, a high-flow mode is used for the center wing fuel tank 11 to reduce the amount of outside air entering the fuel tank, so as to meet the oxygen concentration control requirements of the center wing fuel tank 11 for landing, such as the oxygen concentration after the flight of wide-body aircraft being less than 11% and narrow-body aircraft being less than 12%. During the cruise phase, a low-flow mode is used to reduce the oxygen concentration in the fuel tank to the lowest level, such as 2% to 4%, to provide an ideal initial value for the descent phase.

[0078] The outer wing fuel tanks adopt a single-flow mode, which is achieved through a flow-limiting device with a fixed orifice. The inert gas (in this embodiment, nitrogen-rich gas) is evenly distributed to the left and right outer wing fuel tanks through the distribution branches (outer wing inerting branch L3 and the left outer wing inerting branch L4 and the right outer wing inerting branch L5 branched from the outer wing inerting branch L3). It is only necessary to maintain the oxygen concentration in the fuel tanks below the limit value during the cruise phase, such as 12% to 14.5%.

[0079] According to the aircraft composite fuel tank inerting system of the present invention, the design goal of reducing flammability can be achieved by inerting the outer wing fuel tank only during the cruise phase. The outer wing inerting branch can meet the requirements using low-purity inert gas (NEA in this embodiment). With the inert gas (NEA) flow rate remaining constant, the demand for inert gas (NEA) in the outer wing fuel tank can be reduced. In particular, when the first inert gas generator 2 and the second inert gas generator 3 use hollow fiber membrane ASM, the number of ASMs can be reduced or the diameter of the ASM (hollow fiber membrane) can be reduced, thus reducing the weight of the ASM and the engine bleed air volume (reduced purity, improved nitrogen production efficiency, and reduced engine bleed air volume).

[0080] In one example, after adopting the aircraft composite fuel tank inerting system of this embodiment, the ASM weight was reduced by 26.6% and the engine bleed air volume was reduced by 13.3%.

[0081] <Second Implementation>

[0082] Figure 2 A schematic structural diagram of an aircraft composite fuel tank inerting system according to a second embodiment of the present invention is shown. Hereinafter, the differences from the first embodiment described above will be primarily described, and sometimes the same symbols will be used to denote the same components as in the first embodiment, and repeated descriptions will be omitted. Unless there is a contrary description below or a conflict with other technical features, the features described in the first embodiment also apply to this second embodiment, and will not be described in detail here.

[0083] In this embodiment, a pressure and temperature regulating device 1a is provided upstream of the first inert gas generator 2 in the central wing inerting branch L2. The pressure and temperature regulating device 1a can adjust the pressure (e.g., pressurize) and temperature (e.g., cool) of the gas to be processed from the gas source. The pressure and temperature regulating device 1a includes, for example, a pressure regulating section and a temperature regulating section. Furthermore, the central wing inerting branch L2 is equipped with a first inert gas generator 2.

[0084] A temperature control device 1b is provided in the outer wing inerting branch L3, located upstream of the second inert gas generator 3. The temperature control device 1b is capable of adjusting the temperature of the gas to be processed from the gas source (e.g., cooling it down).

[0085] In this embodiment, the first inert gas generator 2 and the second inert gas generator 3 are respectively adopted as hollow fiber membrane air separation modules (ASM).

[0086] The bleed air pressure regulation design, specifically the bleed air boosting design, can employ electric or turbocharging to improve ASM separation performance and reduce the number of ASMs during descent. In this embodiment, to address the differentiated inerting requirements of the center wing fuel tank and the outer wing fuel tank, the center wing inerting branch L2 adopts a pressure regulation design, specifically a boosting design, while the outer wing inerting branch L3 does not require a pressure regulation design. Thus, the main difference between this embodiment and the first embodiment is that independent upstream bleed air regulation subsystems are set up for the first inert gas generator 2 and the second inert gas generator 3. For the first inert gas generator 2, its bleed air regulation subsystem has temperature and pressure regulation functions. The pressure regulation unit operates during descent to increase the inlet bleed air pressure of the first inert gas generator 2, improving separation performance and reducing the number of ASM components in the first inert gas generator 2. For the second inert gas generator 3, its bleed air regulation subsystem does not require a boosting function, only a temperature regulation function. In addition, for example, because the air separation module operates at a temperature lower than the air source temperature, the temperature control unit (temperature control device) operates throughout the flight.

[0087] <Third Implementation Method>

[0088] Figure 3 A schematic structural diagram of an aircraft composite fuel tank inerting system according to a third embodiment of the present invention is shown. Hereinafter, the differences from the first embodiment will be mainly described, and sometimes the same symbols will be used to denote the same components as in the first embodiment, and repeated descriptions will be omitted. Unless there is a contrary description or conflict with other technical features in the following content, the features described in the first embodiment are also applicable to this third embodiment, and will not be described in detail here.

[0089] In this embodiment, the central wing inerting branch L2 is connected to multiple nozzles 16a, 16b, and 16c at its downstream end. The downstream end of the central wing inerting branch L2 can be connected to multiple nozzles via the multi-branched central wing inert gas distribution branch 19.

[0090] In addition, at least a portion of the left outer wing inerting branch L4 and the right outer wing inerting branch L6 are located outside the central wing fuel tank 11.

[0091] The wing fuel tanks already contain a large number of fuel system and hydraulic system pipelines, and the installation space inside the fuel tanks is limited. In the first embodiment, a portion of the inert gas distribution pipeline (including the left outer wing inertization branch L4 and the right outer wing inertization branch L5, which branch off from the outer wing inertization branch L3) is concentrated in the central wing fuel tank 11 (see reference). Figure 1The installation and layout of the first embodiment presents significant challenges. To address this issue, this implementation method is designed. The main difference between this implementation method and the first embodiment lies in the following: the configuration of the distribution pipeline inside and outside the fuel tank is changed. On the one hand, the ejector pump design at the downstream end of the central wing inerting branch L2 in the first embodiment is replaced with a multi-nozzle design, reducing the installation of equipment inside the fuel tank. On the other hand, a portion of the pipeline network in the inert gas distribution branch of the outer wing fuel tank (outer wing inerting branch L3 and the left outer wing inerting branch L4 and right outer wing inerting branch L5 branching from outer wing inerting branch L3) located in the central wing fuel tank 11 is transferred outside the fuel tank, reducing the installation of pipeline network inside the fuel tank.

[0092] The present invention has been described above by way of example with reference to the accompanying drawings. Obviously, the specific implementation of the present invention is not limited to the above embodiments.

[0093] For example, in the above embodiments, the first inert gas generator and the second inert gas generator respectively use hollow fiber membrane air separation modules, but are not limited thereto. The first inert gas generator and the second inert gas generator may also use other air separation modules, or other inert gas generation methods such as pressure swing adsorption (PSA). The inert gas may be nitrogen, nitrogen-rich gas, carbon dioxide, etc.

[0094] The specific embodiments of the present invention have been described above in conjunction with the accompanying drawings. However, it is understood that the above description does not limit the present invention in any way, and the technical features of each embodiment can be combined with each other in any way to constitute new embodiments. Furthermore, those skilled in the art, after understanding the above specific embodiments, can make various other modifications and changes to the present invention as needed. These do not depart from the essence of the present invention.

Claims

1. An inerting system for aircraft composite fuel tanks, characterized in that, have: Gas distribution pipeline; A central wing inerting branch, which branches off from the gas source distribution line and connects to the central wing fuel tank; and The outer wing inerting branch branch branches off from the air source distribution pipeline and connects to the outer wing fuel tank. The central wing inerting branch is equipped with a first inert gas generator and a multi-flow switching valve. The first inert gas generator receives the gas to be processed from the gas source and generates inert gas. The multi-flow switching valve is located downstream of the first inert gas generator and can switch between a first flow mode and a second flow mode. The flow rate of inert gas provided in the first flow mode is less than the flow rate of inert gas provided in the second flow mode. The outer wing inerting branch is equipped with a second inert gas generator and a first flow limiter. The second inert gas generator receives the gas to be processed from the gas source and generates inert gas. The first flow limiter is located downstream of the second inert gas generator, and a single flow mode is achieved through the first flow limiter. The aircraft composite fuel tank inerting system is configured to inject inert gas into the center wing fuel tank in such a way that the initial oxygen concentration in the center wing fuel tank during the descent phase is below a first upper limit threshold, and to inject inert gas into the outer wing fuel tank in such a way that the oxygen concentration in the outer wing fuel tank during the cruise phase is below a second upper limit threshold that is higher than the first upper limit threshold.

2. The aircraft composite fuel tank inerting system according to claim 1, characterized in that, The gas source distribution pipeline is equipped with an air preparation subsystem, which can regulate the pressure and temperature of the gas source.

3. The aircraft composite fuel tank inerting system according to claim 1, characterized in that, A pressure and temperature regulating device is provided in the central wing inerting branch, upstream of the first inert gas generator. This device can adjust the pressure and temperature of the gas to be treated from the gas source. A temperature control device is provided in the outer wing inerting branch upstream of the second inert gas generator. The temperature control device is capable of adjusting the temperature of the gas to be processed from the gas source.

4. The aircraft composite fuel tank inerting system according to claim 1, characterized in that, The outer wing inerting branch branches off downstream of the first flow restrictor into a left outer wing inerting branch connected to the left outer wing fuel tank and a right outer wing inerting branch connected to the right outer wing fuel tank.

5. The aircraft composite fuel tank inerting system according to claim 4, characterized in that, In the central wing inerting branch, two or more anti-backflow check valves are connected in series at a position downstream of the multi-flow switching valve. An anti-backflow check valve is provided in the outer wing inerting branch at a position downstream of the first flow limiting element and upstream of the bifurcation points of the left and right outer wing inerting branches. Anti-oil cross-contamination check valves are provided in the left and right outer wing inerting branches respectively.

6. The aircraft composite fuel tank inerting system according to claim 4, characterized in that, The central wing inerting branch is connected to multiple nozzles at its downstream end. At least a portion of the left outer wing inerting branch and the right outer wing inerting branch are located outside the central wing fuel tank.

7. The aircraft composite fuel tank inerting system according to claim 1, characterized in that, It also features an ejector air intake system. The central wing inerting branch is connected to the ejector pump at its downstream end, so that the gas in the central wing fuel tank is mixed with the inert gas entering the central wing fuel tank through the ejector inlet pipe before being injected into the central wing fuel tank.

8. The aircraft composite fuel tank inerting system according to claim 1, characterized in that, It also includes a controller that can control the operation of the multi-flow switching valve.

9. The aircraft composite fuel tank inerting system according to claim 1, characterized in that, The first upper limit threshold is below 4%. The second upper limit threshold is below 14.5%.

10. The aircraft composite fuel tank inerting system according to claim 1, characterized in that, The inert gas is a nitrogen-rich gas. The first inert gas generator and the second inert gas generator each use a hollow fiber membrane air separation module. The first flow limiting element is a flow limiting orifice.

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