Test method for matching of flow limiting holes of aircraft fuel tank inerting system

Abstract

The invention belongs to the technical field of aircraft fuel systems, and particularly relates to an aircraft fuel tank inerting system flow limiting hole matching test method. The method comprises the steps that the aircraft fuel tank inerting system is constructed, the aircraft fuel tank inerting system comprises a small-flow inerting branch, a medium-flow inerting branch and a large-flow inerting branch which are arranged in parallel, a small-flow limiting hole is formed in the small-flow inerting branch, a medium-flow limiting hole is formed in the medium-flow inerting branch, and a large-flow limiting hole is formed in the large-flow inerting branch; a large-flow limiting hole is formed in the large-flow inerting branch. The aircraft fuel tank inerting system has a small-flow mode, a medium-flow mode and a large-flow mode. The matching sequence of the small-flow limiting holes, the medium-flow limiting holes and the large-flow limiting holes is determined; respectively determining qualified criteria of the small flow mode, the medium flow mode and the large flow mode; and according to the matching sequence and the corresponding qualification criterion, sequentially carrying out flow limiting hole matching. According to the invention, the flow-limiting hole matching time is saved, and the steps of the flow-limiting hole matching test are simplified.

Description

Technical Field

[0001] The present application belongs to the technical field of aircraft fuel systems, and in particular relates to a flow limiting hole matching test method for an aircraft fuel tank inerting system. Background Art

[0002] Fire or explosion in aircraft fuel system is one of the main causes of aircraft crashes. The fire and explosion prevention capabilities of aircraft fuel system are directly related to aircraft survivability and vulnerability, as well as aircraft utilization, cost and personnel safety. Aircraft fuel tank inerting technology can effectively solve the fire and explosion prevention problems of aircraft fuel system.

[0003] The flow distribution of nitrogen-rich gas in the existing aircraft fuel tank inerting is generally divided into several flow modes. Different flow modes realize the inerting of the aircraft fuel tank through the corresponding inerting branch. The inerting branch is provided with a flow limiting hole. The size of the flow limiting hole is an important factor affecting the inerting effect of the aircraft fuel tank. If the size of the flow limiting hole is too large, the flow corresponding to the flow mode will be too large, and there will be a problem of wasting engine bleed air; if the size of the flow limiting hole is too small, the flow corresponding to the flow mode will be too small, reducing the inerting efficiency of the inerting system for the fuel tank.

[0004] Therefore, it is desired to have a technical solution to overcome or at least alleviate at least one of the above-mentioned defects of the prior art. Summary of the invention

[0005] The purpose of the present application is to provide a flow restriction hole matching test method for an aircraft fuel tank inerting system to solve at least one problem existing in the prior art.

[0006] The technical solution of this application is: A test method for matching flow limiting holes of an aircraft fuel tank inerting system, comprising: Constructing an aircraft fuel tank inerting system, the aircraft fuel tank inerting system comprising a small flow inerting branch, a medium flow inerting branch, and a large flow inerting branch arranged in parallel, the small flow inerting branch being provided with a small flow limiting hole, the medium flow inerting branch being provided with a medium flow limiting hole, the large flow inerting branch being provided with a large flow limiting hole, and the aircraft fuel tank inerting system having a small flow mode, a medium flow mode, and a large flow mode; Determine the matching order of the small flow limiting hole, the medium flow limiting hole, and the large flow limiting hole; Determine the eligibility criteria for small flow mode, medium flow mode, and large flow mode respectively; According to the matching order and the corresponding qualified criteria, the flow limiting holes are matched in sequence.

[0007] Preferably, the aircraft fuel tank inerting system further comprises: An air separation device, wherein the air separation device has an inlet pipeline and an outlet pipeline, the air separation device is connected to an air source through the inlet pipeline, an inlet pressure sensor and an inlet pressure regulating valve are arranged on the inlet pipeline, and a flow sensor and an oxygen concentration sensor are arranged on the outlet pipeline; A fuel tank, wherein a fuel tank pressure sensor is provided on the fuel tank; The two ends of the small flow inerting branch are respectively connected to the outlet pipeline of the air separation device and the oil tank; The two ends of the medium flow inerting branch are respectively connected to the outlet pipeline of the air separation device and the oil tank, and a medium flow cut-off valve is also provided on the medium flow inerting branch; The two ends of the large flow inerting branch are respectively connected to the outlet pipeline of the air separation device and the oil tank, and a large flow cut-off valve is also arranged on the large flow inerting branch; A controller is used to collect data fed back by various sensors and control the inlet pressure regulating valve, the medium flow cut-off valve and the large flow cut-off valve.

[0008] Preferably, After the aircraft fuel tank inerting system is started on the ground, the air separation device is preheated, and after the preheating is completed, the medium flow mode is entered; During the aircraft climbing and cruising phases, the aircraft fuel tank inerting system enters a low-flow mode; During the aircraft's descent phase, the aircraft fuel tank inerting system enters high-flow mode; In a low flow mode, the aircraft fuel tank is inerted through the low flow inerting branch; In the medium flow mode, the medium flow cut-off valve is opened, and the aircraft fuel tank is inerted through the small flow inerting branch and the medium flow inerting branch; In the large flow mode, the large flow cut-off valve is opened, and the aircraft fuel tank is inerted through the small flow inerting branch and the large flow inerting branch.

[0009] Preferably, the first qualification criterion of the small flow mode is: the oxygen concentration of the nitrogen-rich gas in the small flow mode is between O1±0.3%, wherein O1 is the oxygen concentration corresponding to the small flow mode.

[0010] Preferably, the second qualification criterion of the medium flow mode is: the oxygen concentration of the nitrogen-rich gas in the medium flow mode is between O2±0.3%, wherein O2 is the oxygen concentration corresponding to the medium flow mode.

[0011] Preferably, the third qualification criterion of the large flow mode is: the nitrogen-rich gas flow rate in the large flow mode is in the descending stage of the design profile of the aircraft fuel tank inerting system, and the pressure of the fuel tank relative to the atmospheric environment is Pmin kPa~(P min +2) kPa, where P min The minimum negative pressure designed for aircraft fuel tank inerting systems.

[0012] Preferably, the small flow limiting hole matching process is as follows: S1. Determine the initial size of the three flow restriction holes and install the aircraft fuel tank inerting system; S2. Start the aircraft fuel tank inerting system, and introduce high-temperature gas into the aircraft fuel tank inerting system through the gas source to preheat the air separation device; S3. After the air separation unit is fully preheated, the aircraft fuel tank inerting system enters the medium flow mode; S4, adjusting the air separation device inlet pressure to a second pressure, where the second pressure is the bleed air pressure after the ground auxiliary power unit APU is started; S5. After the inlet pressure is stable, record the nitrogen-rich gas flow rate and oxygen concentration at the outlet of the air separation unit in the medium flow mode; S6. Set the wheel load to air, and the aircraft fuel tank inerting system enters low flow mode; S7, adjusting the inlet pressure of the air separation device to a first pressure, where the first pressure is the minimum bleed air pressure when the aircraft is cruising at high altitude; S8. After the inlet pressure is stable, record the nitrogen-rich gas flow rate and oxygen concentration at the outlet of the air separation unit in the low-flow mode; S9, comparing the oxygen concentration of the nitrogen-rich gas in the low flow mode with the first qualification criterion, if the first qualification criterion is not met, executing the following steps: S9.1. Turn off the aircraft fuel tank inerting system; S9.2. Adjust the size of the low-flow restrictor orifice and reinstall the aircraft fuel tank inerting system; S9.3, adjust the size of the medium flow limiting hole, reinstall the aircraft fuel tank inerting system, and return to step S2; Repeat steps S2-S9 until the first qualification criterion is met and the small flow limiting hole matching is completed.

[0013] Preferably, In step S9.2, the process of adjusting the size of the small flow limiting hole specifically includes: S9.2.1. If the oxygen concentration of the nitrogen-rich gas in the low-flow mode is higher than O1+0.3%, reduce the size of the low-flow limiting orifice; S9.2.2. If the oxygen concentration of the nitrogen-rich gas in the low-flow mode is lower than O1-0.3%, increase the size of the low-flow limiting orifice.

[0014] Preferably, In step S9.3, the process of adjusting the size of the medium flow limiting hole specifically includes: S9.3.1. If the oxygen concentration of the nitrogen-rich gas in the medium flow mode is between O2±0.3%, when the size of the small flow limiting hole is reduced, the size of the medium flow limiting hole is increased; when the size of the small flow limiting hole is increased, the size of the medium flow limiting hole is decreased; S9.3.2. If the oxygen concentration of the nitrogen-rich gas in the medium flow mode is higher than O2+0.3%, when the size of the small flow limiting hole is reduced, the size of the medium flow limiting hole is reduced or remains unchanged; when the size of the small flow limiting hole is increased, the size of the medium flow limiting hole is reduced; S9.3.3. If the oxygen concentration of the nitrogen-rich gas in the medium flow mode is lower than O2-0.3%, when the size of the small flow limiting hole is reduced, the size of the medium flow limiting hole shall be increased; when the size of the small flow limiting hole is increased, the size of the medium flow limiting hole shall be increased or remain unchanged.

[0015] Preferably, the medium flow limiting hole matching process is as follows: S10, comparing the oxygen concentration of the nitrogen-rich gas in the medium flow mode with the second qualification criterion, if the second qualification criterion is not met, executing the following steps: S10.1. Turn off the aircraft fuel tank inerting system; S10.2. Adjust the size of the medium flow restrictor orifice and reinstall the aircraft fuel tank inerting system; S10.3. Start the aircraft fuel tank inerting system and introduce high-temperature gas into the aircraft fuel tank inerting system through the gas source to preheat the air separation device; S10.4. After the air separation unit is fully preheated, the aircraft fuel tank inerting system enters the medium flow mode; S10.5. Adjust the inlet pressure of the air separation unit to the second pressure; S10.6. After the inlet pressure is stabilized, record the nitrogen-rich gas flow rate and oxygen concentration at the outlet of the air separation unit in the medium flow mode, and return to step S10; Repeat step S10 until the second qualification criterion is met, and the matching of the medium flow limiting hole is completed.

[0016] Preferably, In step S10.2, the process of adjusting the size of the medium flow limiting hole specifically includes: S10.2.1. If the oxygen concentration of the nitrogen-rich gas in the medium flow mode is higher than O2+0.3%, reduce the size of the medium flow limiting orifice; S10.2.2. If the oxygen concentration of the nitrogen-rich gas in the medium flow mode is lower than O2-0.3%, increase the size of the medium flow limiting orifice.

[0017] Preferably, the large flow limiting hole matching process is as follows: S11, setting the wheel load to air, and simulating the aircraft to climb and descend according to the designed profile; S12. Before the aircraft descends, the inlet pressure of the air separation device is adjusted to a third pressure, where the third pressure is the average bleed air pressure during the aircraft's descent phase; S13, during the descent phase, the aircraft fuel tank inerting system enters the high flow mode; S14, after the inlet pressure is stabilized, record the minimum pressure of the fuel tank in the large flow mode, as well as the nitrogen-rich gas flow and oxygen concentration at the outlet of the air separation unit; S15, comparing the minimum pressure of the fuel tank in the large flow mode with the third qualification criterion, if the third qualification criterion is not met, executing the following steps: S15.1. Turn off the aircraft fuel tank inerting system; S15.2. Adjust the size of the high flow restrictor orifice and reinstall the aircraft fuel tank inerting system; S15.3. Start the aircraft fuel tank inerting system and introduce high-temperature or normal-temperature gas into the aircraft fuel tank inerting system through the gas source to preheat the air separation device; S15.4, after the air separation device is fully preheated, return to step S11; Repeat steps S11-S15 until the third qualification criterion is met, and then proceed to step S16; S16, determining whether the gas introduced by the gas source to the aircraft fuel tank inerting system in the large flow mode is high temperature gas, if so, proceeding to step S17, if not, executing the following steps: S16.1. Turn off the aircraft fuel tank inerting system; S16.2. Start the aircraft fuel tank inerting system and introduce high-temperature or normal-temperature gas into the aircraft fuel tank inerting system through the gas source to preheat the air separation device; S16.3, after the air separation device is fully preheated, return to step S11; S17. Turn off the aircraft fuel tank inerting system and complete the matching of the large flow limiting orifice.

[0018] Preferably, In step S15.2, the process of adjusting the size of the large flow limiting hole specifically includes: S15.2.1. If the minimum pressure of the fuel tank in the high flow mode during the descent phase is less than P min kPa, increase the size of the large flow limiting hole; S15.2.2. If the minimum pressure of the fuel tank in the high flow mode during the descent phase is greater than (P min +2) kPa, reduce the size of the large flow limiting hole.

[0019] The invention has at least the following beneficial technical effects: The aircraft fuel tank inerting system flow limiting hole matching test method of the present application constructs an aircraft fuel tank inerting system, clarifies the flow limiting hole matching sequence in small flow, medium flow and large flow modes, and the qualified criteria for flow limiting hole matching in different flow modes, and provides the optimal process of flow limiting hole matching in combination with the usage scenarios, obtains the optimal sizes of different flow limiting holes, saves the time of flow limiting hole matching, and simplifies the steps of the flow limiting hole matching test. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a flow chart of a flow restriction hole matching test method of an aircraft fuel tank inerting system according to one embodiment of the present application; Figure 2 It is a schematic cross-sectional diagram of a large flow limiting hole matching according to an embodiment of the present application. DETAILED DESCRIPTION

[0021] In order to make the purpose, technical scheme and advantages of the implementation of this application clearer, the technical scheme in the embodiment of this application will be described in more detail below in conjunction with the drawings in the embodiment of this application. In the drawings, the same or similar reference numerals throughout represent the same or similar elements or elements with the same or similar functions. The described embodiments are part of the embodiments of this application, not all of them. The embodiments described below with reference to the drawings are exemplary and are intended to be used to explain this application, and should not be construed as limitations on this application. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application. The embodiments of this application are described in detail below in conjunction with the drawings.

[0022] The following is combined with Figure 1 To Attachment Figure 2 This application is described in further detail.

[0023] The present application provides a flow restriction hole matching test method for an aircraft fuel tank inerting system, comprising the following steps: Constructing an aircraft fuel tank inerting system, the aircraft fuel tank inerting system comprising a small flow inerting branch, a medium flow inerting branch, and a large flow inerting branch arranged in parallel, the small flow inerting branch being provided with a small flow limiting hole, the medium flow inerting branch being provided with a medium flow limiting hole, the large flow inerting branch being provided with a large flow limiting hole, and the aircraft fuel tank inerting system having a small flow mode, a medium flow mode, and a large flow mode; Determine the matching order of the small flow limiting hole, the medium flow limiting hole, and the large flow limiting hole; Determine the eligibility criteria for small flow mode, medium flow mode, and large flow mode respectively; According to the matching order and the corresponding qualified criteria, the flow limiting holes are matched in sequence.

[0024] The aircraft fuel tank inerting system limiting hole matching test method of the present application, in order to meet the use requirements of nitrogen-rich gas in different aircraft working conditions, a certain type of aircraft fuel tank inerting system is set with three inerting flow modes, namely small flow mode, medium flow mode, and large flow mode. These three flow modes respectively achieve different nitrogen-rich gas flow rates and oxygen concentrations through three different limiting holes. After the aircraft fuel tank inerting system is started on the ground, the air separation device needs to be preheated, and after the preheating is completed, it enters the medium flow mode; after the aircraft takes off, the aircraft fuel tank inerting system enters the small flow mode during the aircraft climbing stage and the aircraft cruising stage; during the aircraft descending stage, the aircraft fuel tank inerting system enters the large flow mode.

[0025] In a preferred embodiment of the present application, the aircraft fuel tank inerting system further includes: an air separation device, a fuel tank, a controller, etc. The air separation device has an inlet pipeline and an outlet pipeline, the air separation device is connected to the gas source through the inlet pipeline, an inlet pressure sensor and an inlet pressure regulating valve are arranged on the inlet pipeline, and a flow sensor and an oxygen concentration sensor are arranged on the outlet pipeline; a fuel tank pressure sensor is arranged on the fuel tank; the two ends of the small flow inerting branch are respectively connected to the outlet pipeline of the air separation device and the fuel tank; the two ends of the medium flow inerting branch are respectively connected to the outlet pipeline of the air separation device and the fuel tank, and a medium flow cut-off valve is also arranged on the medium flow inerting branch; the two ends of the large flow inerting branch are respectively connected to the outlet pipeline of the air separation device and the fuel tank, and a large flow cut-off valve is also arranged on the large flow inerting branch; the controller is used to collect data fed back by each sensor, and control the inlet pressure regulating valve, the medium flow cut-off valve and the large flow cut-off valve.

[0026] The aircraft fuel tank inerting system flow limiting hole matching test method of the present application, the three flow modes of the aircraft fuel tank inerting system correspond to different inerting branches, the small flow inerting branch is a normally open pipeline, the on-off of the medium flow inerting branch is controlled by the medium flow cut-off valve, and the on-off of the large flow inerting branch is controlled by the large flow cut-off valve. Therefore, in the small flow mode, the aircraft fuel tank is inerted through the small flow inerting branch; in the medium flow mode, the medium flow cut-off valve is opened, and the aircraft fuel tank is inerted through the small flow inerting branch and the medium flow inerting branch; in the large flow mode, the large flow cut-off valve is opened, and the aircraft fuel tank is inerted through the small flow inerting branch and the large flow inerting branch.

[0027] In the aircraft fuel tank inerting system flow limiting hole matching test method of the present application, the medium flow mode corresponds to the sum of the flow rates flowing through the small flow inerting branch and the medium flow inerting branch, and the large flow mode corresponds to the sum of the flow rates flowing through the small flow inerting branch and the large flow inerting branch. For this reason, combined with the different start-up timings of the three flow modes during flight, the matching order of the flow limiting holes is determined as follows: first match the small flow limiting hole, then match the medium flow limiting hole, and finally match the large flow limiting hole.

[0028] The aircraft fuel tank inerting system flow limiting hole matching test method of the present application further obtains the qualified criteria under three flow modes. Among them, the main purpose of the small flow mode is to fill the gas phase space of the fuel tank with high-quality nitrogen-rich gas to minimize the oxygen concentration in the gas phase space of the fuel tank, so as to ensure that the oxygen concentration in the fuel tank can meet the design requirements after the low-quality nitrogen-rich gas is filled in the aircraft descent stage. Therefore, the qualified criterion for the flow limiting hole matching of the small flow mode should be: the oxygen concentration of the nitrogen-rich gas in the small flow mode is between O1±0.3%, which is the first qualified criterion, wherein O1 is the oxygen concentration corresponding to the small flow mode. The purpose of the medium flow mode is to reduce the initial oxygen concentration of the gas phase space of the fuel tank to the design value within the specified time; when the oxygen concentration of the nitrogen-rich gas is O2, the oxygen concentration of the fuel tank can be reduced to the design value in the fastest time. Therefore, the qualified criterion for the flow limiting hole matching of the medium flow mode should be: the oxygen concentration of the nitrogen-rich gas in the medium flow mode is between O2±0.3%, which is the second qualified criterion, wherein O2 is the oxygen concentration corresponding to the medium flow mode. The primary purpose of the large flow mode is to ensure that the negative pressure of the fuel tank does not exceed the limit, and the secondary purpose is to reduce the oxygen concentration in the gas phase space of the fuel tank. Once the negative pressure of the fuel tank exceeds the limit, the anti-vacuum valve in the breather box connected to the fuel tank will open, and a large amount of external air will enter the gas phase space of the fuel tank. The oxygen concentration in the gas phase space of the fuel tank cannot be guaranteed. Therefore, the qualified criterion for matching the flow limiting hole in the large flow mode should be: the nitrogen-rich gas flow rate in the large flow mode should be guaranteed in the descending stage of the design profile of the aircraft fuel tank inerting system, and the pressure of the fuel tank relative to the atmospheric environment is P min kPa~(P min +2) kPa, which is the third qualified criterion. The fuel tank has a 2kPa margin relative to the atmospheric pressure to avoid the difference between the test and the actual flight, which may lead to the over-limit of the fuel tank pressure. min The minimum negative pressure designed for the aircraft fuel tank inerting system. The descent phase corresponding to the design profile of the aircraft fuel tank inerting system has the highest altitude at the descent starting point and the fastest average descent speed.

[0029] The aircraft fuel tank inerting system flow limiting hole matching test method of the present application, after determining the flow limiting hole matching sequence and the qualified criteria of different flow modes, flow limiting hole matching is performed in sequence. Before the flow limiting hole matching, the sizes of the three flow limiting holes are determined in advance by calculation and the aircraft fuel tank inerting system is installed. The air separation device preferably uses a hollow fiber membrane, which has the best performance under high temperature conditions.

[0030] The operation steps for matching the small flow limiting hole are as follows: start the aircraft fuel tank inerting system, introduce high-temperature gas into the aircraft fuel tank inerting system, first fully preheat the air separation device, and after the air separation device is fully preheated, the aircraft fuel tank inerting system automatically enters the medium flow mode, adjusts the bleed air pressure at the inlet of the air separation device to the second pressure, and records the nitrogen-rich gas flow and oxygen concentration in the medium flow mode; set the wheel load to air, the aircraft fuel tank inerting system enters the small flow mode, adjusts the bleed air pressure at the inlet of the air separation device to the first pressure, and records the nitrogen-rich gas flow and oxygen concentration in the small flow mode. The oxygen concentration of the nitrogen-rich gas in the small flow mode is compared with the first qualified criterion. If the first qualified criterion is not met, the aircraft fuel tank inerting system is turned off and the size of the small flow limiting hole is adjusted. The adjustment principle is: if the oxygen concentration in the small flow mode is too high, the size of the small flow limiting hole is reduced; if the oxygen concentration in the small flow mode is too low, the size of the small flow limiting hole is increased; after adjusting the size of the small flow limiting hole, reinstall it; further, adjust the size of the medium flow limiting hole. The adjustment principle is: compare the oxygen concentration of the nitrogen-rich gas in the medium flow mode with the second qualified criterion. If the second qualified criterion is met, when the small flow limiting hole is reduced, the size of the medium flow limiting hole is increased; when the small flow limiting hole is increased, the size of the medium flow limiting hole is increased. Reduce the size; if the second qualified criterion is not met, when the oxygen concentration in the medium flow mode is high and the small flow limiting hole is reduced, adjust the size of the medium flow limiting hole as needed; when the oxygen concentration in the medium flow mode is high and the small flow limiting hole is increased, reduce the size of the medium flow limiting hole; if the second qualified criterion is not met, when the oxygen concentration in the medium flow mode is low and the small flow limiting hole is reduced, increase the size of the medium flow limiting hole; when the oxygen concentration in the medium flow mode is low and the small flow limiting hole is increased, adjust the size of the medium flow limiting hole as needed; reinstall the size of the medium flow limiting hole after adjusting it, and continue the test by reinstalling the small flow limiting hole matching operation steps until the first qualified criterion is met and the small flow limiting hole matching is completed.

[0031] The medium flow limiting hole matching operation steps are as follows: compare the oxygen concentration of the nitrogen-rich gas in the medium flow mode with the second qualified criterion. If the second qualified criterion is not met, close the aircraft fuel tank inerting system and adjust the size of the medium flow limiting hole. The adjustment principle is: when the oxygen concentration in the medium flow mode is high, reduce the size of the medium flow limiting hole; when the oxygen concentration in the medium flow mode is low, increase the size of the medium flow limiting hole; reinstall after adjusting the size of the medium flow limiting hole, start the aircraft fuel tank inerting system and introduce high-temperature gas, and after the air separation unit is preheated, enter the medium flow mode, adjust the bleed air pressure at the inlet of the air separation unit to the second pressure, and record the nitrogen-rich gas flow and oxygen concentration in the medium flow mode. Repeat the medium flow limiting hole matching operation steps until the second qualified criterion is met and the medium flow limiting hole matching is completed.

[0032] The operation steps of matching the large flow limiting hole are as follows: set the aircraft wheel load to the air, and simulate the aircraft climbing and descending according to the designed profile, wherein the atmospheric environment pressure of the fuel tank changes according to the height corresponding to the designed profile; before the aircraft descends, adjust the bleed air pressure at the inlet of the air separation device to the third pressure; during the descent phase, the aircraft fuel tank inerting system enters the large flow mode, records the minimum pressure of the fuel tank under the large flow mode during the descent phase, as well as the flow rate and oxygen concentration of the nitrogen-rich gas, and compares the minimum pressure with the third qualified criterion. If the third qualified criterion is met, the large flow limiting hole is matched. End; if the third qualified criterion is not met, the aircraft fuel tank inerting system is turned off, and the large flow limiting hole size is adjusted. The adjustment principle is: when the minimum pressure of the fuel tank is lower than the third qualified criterion, the large flow limiting hole size is increased; when the minimum pressure of the fuel tank is greater than the third qualified criterion, the large flow limiting hole size is reduced; after adjusting the large flow limiting hole size, reinstall it, start the aircraft fuel tank inerting system, and pass high-temperature or normal temperature gas. After the air separation device is preheated, repeat the large flow limiting hole matching operation steps until the third qualified criterion is met and the large flow limiting hole matching is completed. It can be understood that in order to shorten the limiting hole matching time, the large flow limiting hole matching can pass normal temperature pressurized gas. After the large flow limiting hole size is confirmed, the high temperature pressurized gas is passed to confirm the oxygen concentration corresponding to the large flow mode.

[0033] In a specific embodiment of the present application, Figure 1 , the limiting hole matching process is introduced in detail: S1. Determine the initial size of the three flow restriction holes and install the aircraft fuel tank inerting system; S2. Start the aircraft fuel tank inerting system, and introduce high-temperature gas into the aircraft fuel tank inerting system through the gas source to preheat the air separation device; S3. After the air separation unit is fully preheated, the aircraft fuel tank inerting system enters the medium flow mode; S4, adjusting the air separation device inlet pressure to a second pressure, where the second pressure is the bleed air pressure after the ground auxiliary power unit APU is started; The ground auxiliary power unit APU is similar to a kerosene generator, which is used to provide air conditioning and onboard power supply, as well as to start the engine when the engine is not started. The ground inerting gas source comes from environmental control. There are generally two sources of environmental control bleed air, the ground auxiliary power unit APU or the engine. The bleed air pressure of the ground auxiliary power unit APU is lower than the engine bleed air pressure. The lower the pressure, the more stringent the air separation performance assessment. Therefore, the bleed air pressure after the ground auxiliary power unit APU is started is selected as the matching pressure of the medium flow.

[0034] S5. After the inlet pressure is stable, record the nitrogen-rich gas flow rate and oxygen concentration at the outlet of the air separation unit in the medium flow mode; S6. Set the wheel load to air, and the aircraft fuel tank inerting system enters low flow mode; S7, adjusting the inlet pressure of the air separation device to a first pressure, where the first pressure is the minimum bleed air pressure when the aircraft is cruising at high altitude; S8. After the inlet pressure is stable, record the nitrogen-rich gas flow rate and oxygen concentration at the outlet of the air separation unit in the low-flow mode; S9, comparing the oxygen concentration of the nitrogen-rich gas in the low flow mode with the first qualification criterion, if the first qualification criterion is not met, executing the following steps: S9.1. Turn off the aircraft fuel tank inerting system; S9.2. Adjust the size of the low-flow restrictor orifice and reinstall the aircraft fuel tank inerting system; The process of adjusting the size of the low flow restrictor orifice includes: S9.2.1. If the oxygen concentration of the nitrogen-rich gas in the low-flow mode is higher than O1+0.3%, reduce the size of the low-flow limiting orifice; S9.2.2. If the oxygen concentration of the nitrogen-rich gas in the low-flow mode is lower than O1-0.3%, increase the size of the low-flow limiting orifice; S9.3, adjust the size of the medium flow limiting hole, reinstall the aircraft fuel tank inerting system, and return to step S2; The process of adjusting the size of the medium flow restrictor orifice includes: S9.3.1. If the oxygen concentration of the nitrogen-rich gas in the medium flow mode is between O2±0.3%, when the size of the small flow limiting hole is reduced, the size of the medium flow limiting hole is increased; when the size of the small flow limiting hole is increased, the size of the medium flow limiting hole is decreased; S9.3.2. If the oxygen concentration of the nitrogen-rich gas in the medium flow mode is higher than O2+0.3%, when the size of the small flow limiting hole is reduced, the size of the medium flow limiting hole is reduced or remains unchanged; when the size of the small flow limiting hole is increased, the size of the medium flow limiting hole is reduced; S9.3.3. If the oxygen concentration of the nitrogen-rich gas in the medium flow mode is lower than O2-0.3%, when the size of the small flow limiting hole is reduced, the size of the medium flow limiting hole is increased; when the size of the small flow limiting hole is increased, the size of the medium flow limiting hole is increased or remains unchanged; Repeat steps S2-S9 until the first qualification criterion is met and the small flow limiting hole matching is completed.

[0035] S10, comparing the oxygen concentration of the nitrogen-rich gas in the medium flow mode with the second qualification criterion, if the second qualification criterion is not met, executing the following steps: S10.1. Turn off the aircraft fuel tank inerting system; S10.2. Adjust the size of the medium flow restrictor orifice and reinstall the aircraft fuel tank inerting system; The process of adjusting the size of the medium flow restrictor orifice includes: S10.2.1. If the oxygen concentration of the nitrogen-rich gas in the medium flow mode is higher than O2+0.3%, reduce the size of the medium flow limiting orifice; S10.2.2. If the oxygen concentration of the nitrogen-rich gas in the medium flow mode is lower than O2-0.3%, increase the size of the medium flow limiting orifice; S10.3. Start the aircraft fuel tank inerting system and introduce high-temperature gas into the aircraft fuel tank inerting system through the gas source to preheat the air separation device; S10.4. After the air separation unit is fully preheated, the aircraft fuel tank inerting system enters the medium flow mode; S10.5. Adjust the inlet pressure of the air separation unit to the second pressure; S10.6. After the inlet pressure is stabilized, record the nitrogen-rich gas flow rate and oxygen concentration at the outlet of the air separation unit in the medium flow mode, and return to step S10; Repeat step S10 until the second qualification criterion is met, and the matching of the medium flow limiting hole is completed.

[0036] S11, set the wheel load to air, and simulate the aircraft according to the design profile (such as Figure 2 Perform a climb descent as shown; S12. Before the aircraft descends, the inlet pressure of the air separation device is adjusted to a third pressure, where the third pressure is the average bleed air pressure during the aircraft's descent phase; S13, during the descent phase, the aircraft fuel tank inerting system enters the high flow mode; S14, after the inlet pressure is stabilized, record the minimum pressure of the fuel tank in the large flow mode, as well as the nitrogen-rich gas flow and oxygen concentration at the outlet of the air separation unit; S15, comparing the minimum pressure of the fuel tank in the large flow mode with the third qualification criterion, if the third qualification criterion is not met, executing the following steps: S15.1. Turn off the aircraft fuel tank inerting system; S15.2. Adjust the size of the high flow restrictor orifice and reinstall the aircraft fuel tank inerting system; The process of adjusting the size of the high flow restriction orifice includes: S15.2.1. If the minimum pressure of the fuel tank in the high flow mode during the descent phase is less than P min kPa, increase the size of the large flow limiting hole; S15.2.2. If the minimum pressure of the fuel tank in the high flow mode during the descent phase is greater than (P min +2) kPa, reduce the size of the large flow limiting hole; S15.3. Start the aircraft fuel tank inerting system and introduce high-temperature or normal-temperature gas into the aircraft fuel tank inerting system through the gas source to preheat the air separation device; S15.4, after the air separation device is fully preheated, return to step S11; Repeat steps S11-S15 until the third qualification criterion is met, and then proceed to step S16; S16, determining whether the gas introduced by the gas source to the aircraft fuel tank inerting system in the large flow mode is high temperature gas, if so, proceeding to step S17, if not, executing the following steps: S16.1. Turn off the aircraft fuel tank inerting system; S16.2. Start the aircraft fuel tank inerting system and introduce high-temperature or normal-temperature gas into the aircraft fuel tank inerting system through the gas source to preheat the air separation device; S16.3, after the air separation device is fully preheated, return to step S11; S17. Turn off the aircraft fuel tank inerting system and complete the matching of the large flow limiting orifice.

[0037] The aircraft fuel tank inerting system flow limiting hole matching test method of the present application constructs an aircraft fuel tank inerting system with three flow modes according to the use requirements of different aircraft working conditions. The three flow modes correspond to nitrogen-rich gases with three different oxygen concentrations and flow rates, and the nitrogen-rich gases in the three flow modes are all ensured by flow limiting holes of different sizes. Since the small flow inerting branch is a normally open pipeline, it is necessary to first match the small flow flow limiting hole, and then match the medium flow flow limiting hole and the large flow flow limiting hole. According to the main purpose of different flow modes, the qualified criterion for the matching of flow limiting holes of different flow modes is given. Combined with the usage scenarios, the optimal process of flow limiting hole matching is given, and the optimal sizes of different flow limiting holes are obtained, which saves the time of flow limiting hole matching and simplifies the steps of the flow limiting hole matching test.

[0038] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application shall be based on the protection scope of the claims.

Claims

1. A test method for matching flow restriction holes of an aircraft fuel tank inerting system, characterized in that: include: Constructing an aircraft fuel tank inerting system, the aircraft fuel tank inerting system comprising a small flow inerting branch, a medium flow inerting branch, and a large flow inerting branch arranged in parallel, the small flow inerting branch being provided with a small flow limiting hole, the medium flow inerting branch being provided with a medium flow limiting hole, the large flow inerting branch being provided with a large flow limiting hole, and the aircraft fuel tank inerting system having a small flow mode, a medium flow mode, and a large flow mode; Determine the matching order of the small flow limiting hole, the medium flow limiting hole, and the large flow limiting hole; Determine the eligibility criteria for small flow mode, medium flow mode, and large flow mode respectively; According to the matching order and the corresponding qualified criteria, the flow limiting holes are matched in sequence.

2. The aircraft fuel tank inerting system flow restriction hole matching test method according to claim 1 is characterized in that: The aircraft fuel tank inerting system also includes: An air separation device, wherein the air separation device has an inlet pipeline and an outlet pipeline, the air separation device is connected to an air source through the inlet pipeline, an inlet pressure sensor and an inlet pressure regulating valve are arranged on the inlet pipeline, and a flow sensor and an oxygen concentration sensor are arranged on the outlet pipeline; A fuel tank, wherein a fuel tank pressure sensor is provided on the fuel tank; The two ends of the small flow inerting branch are respectively connected to the outlet pipeline of the air separation device and the oil tank; The two ends of the medium flow inerting branch are respectively connected to the outlet pipeline of the air separation device and the oil tank, and a medium flow cut-off valve is also provided on the medium flow inerting branch; The two ends of the large flow inerting branch are respectively connected to the outlet pipeline of the air separation device and the oil tank, and a large flow cut-off valve is also arranged on the large flow inerting branch; A controller is used to collect data fed back by various sensors and control the inlet pressure regulating valve, the medium flow cut-off valve and the large flow cut-off valve.

3. The aircraft fuel tank inerting system flow restriction hole matching test method according to claim 2 is characterized in that: After the aircraft fuel tank inerting system is started on the ground, the air separation device is preheated, and after the preheating is completed, the medium flow mode is entered; During the aircraft climbing and cruising phases, the aircraft fuel tank inerting system enters a low-flow mode; During the aircraft's descent phase, the aircraft fuel tank inerting system enters high-flow mode; In a low flow mode, the aircraft fuel tank is inerted through the low flow inerting branch; In the medium flow mode, the medium flow cut-off valve is opened, and the aircraft fuel tank is inerted through the small flow inerting branch and the medium flow inerting branch; In the large flow mode, the large flow cut-off valve is opened, and the aircraft fuel tank is inerted through the small flow inerting branch and the large flow inerting branch.

4. The aircraft fuel tank inerting system flow restriction hole matching test method according to claim 3 is characterized in that: The first qualification criterion of the low flow mode is that the oxygen concentration of the nitrogen-rich gas in the low flow mode is between O1±0.3%, where O1 is the oxygen concentration corresponding to the low flow mode.

5. The aircraft fuel tank inerting system flow restriction hole matching test method according to claim 4, characterized in that: The second qualification criterion of the medium flow mode is that the oxygen concentration of the nitrogen-rich gas in the medium flow mode is between O2±0.3%, where O2 is the oxygen concentration corresponding to the medium flow mode.

6. The aircraft fuel tank inerting system flow restriction hole matching test method according to claim 5, characterized in that: The third qualification criterion of the large flow mode is: the nitrogen-rich gas flow rate in the large flow mode is in the descending stage of the design profile of the aircraft fuel tank inerting system, and the pressure of the fuel tank relative to the atmospheric environment is P min kPa~(P min +2) kPa, where P min The minimum negative pressure designed for aircraft fuel tank inerting systems.

7. The aircraft fuel tank inerting system flow restriction hole matching test method according to claim 6, characterized in that: The matching process of small flow limiting holes is as follows: S1. Determine the initial size of the three flow restriction holes and install the aircraft fuel tank inerting system; S2. Start the aircraft fuel tank inerting system, and introduce high-temperature gas into the aircraft fuel tank inerting system through the gas source to preheat the air separation device; S3. After the air separation unit is fully preheated, the aircraft fuel tank inerting system enters the medium flow mode; S4, adjusting the air separation device inlet pressure to a second pressure, where the second pressure is the bleed air pressure after the ground auxiliary power unit APU is started; S5. After the inlet pressure is stable, record the nitrogen-rich gas flow rate and oxygen concentration at the outlet of the air separation unit in the medium flow mode; S6. Set the wheel load to air, and the aircraft fuel tank inerting system enters low flow mode; S7, adjusting the inlet pressure of the air separation device to a first pressure, where the first pressure is the minimum bleed air pressure when the aircraft is cruising at high altitude; S8. After the inlet pressure is stable, record the nitrogen-rich gas flow rate and oxygen concentration at the outlet of the air separation unit in the low-flow mode; S9, comparing the oxygen concentration of the nitrogen-rich gas in the low flow mode with the first qualification criterion, if the first qualification criterion is not met, executing the following steps: S9.

1. Turn off the aircraft fuel tank inerting system; S9.

2. Adjust the size of the low-flow restrictor orifice and reinstall the aircraft fuel tank inerting system; S9.3, adjust the size of the medium flow limiting hole, reinstall the aircraft fuel tank inerting system, and return to step S2; Repeat steps S2-S9 until the first qualification criterion is met and the small flow limiting hole matching is completed.

8. The aircraft fuel tank inerting system flow restriction hole matching test method according to claim 7, characterized in that: In step S9.2, the process of adjusting the size of the small flow limiting hole specifically includes: S9.2.

1. If the oxygen concentration of the nitrogen-rich gas in the low-flow mode is higher than O1+0.3%, reduce the size of the low-flow limiting orifice; S9.2.

2. If the oxygen concentration of the nitrogen-rich gas in the low-flow mode is lower than O1-0.3%, increase the size of the low-flow limiting orifice.

9. The aircraft fuel tank inerting system flow restriction hole matching test method according to claim 8, characterized in that: In step S9.3, the process of adjusting the size of the medium flow limiting hole specifically includes: S9.3.

1. If the oxygen concentration of the nitrogen-rich gas in the medium flow mode is between O2±0.3%, when the size of the small flow limiting hole is reduced, the size of the medium flow limiting hole is increased; when the size of the small flow limiting hole is increased, the size of the medium flow limiting hole is decreased; S9.3.

2. If the oxygen concentration of the nitrogen-rich gas in the medium flow mode is higher than O2+0.3%, when the size of the small flow limiting hole is reduced, the size of the medium flow limiting hole is reduced or remains unchanged; when the size of the small flow limiting hole is increased, the size of the medium flow limiting hole is reduced; S9.3.

3. If the oxygen concentration of the nitrogen-rich gas in the medium flow mode is lower than O2-0.3%, when the size of the small flow limiting hole is reduced, the size of the medium flow limiting hole shall be increased; when the size of the small flow limiting hole is increased, the size of the medium flow limiting hole shall be increased or remain unchanged.

10. The aircraft fuel tank inerting system flow restriction hole matching test method according to claim 9, characterized in that: The matching process of medium flow limiting hole is as follows: S10, comparing the oxygen concentration of the nitrogen-rich gas in the medium flow mode with the second qualification criterion, if the second qualification criterion is not met, executing the following steps: S10.

1. Turn off the aircraft fuel tank inerting system; S10.

2. Adjust the size of the medium flow restrictor orifice and reinstall the aircraft fuel tank inerting system; S10.

3. Start the aircraft fuel tank inerting system and introduce high-temperature gas into the aircraft fuel tank inerting system through the gas source to preheat the air separation device; S10.

4. After the air separation unit is fully preheated, the aircraft fuel tank inerting system enters the medium flow mode; S10.

5. Adjust the inlet pressure of the air separation unit to the second pressure; S10.

6. After the inlet pressure is stabilized, record the nitrogen-rich gas flow rate and oxygen concentration at the outlet of the air separation unit in the medium flow mode, and return to step S10; Repeat step S10 until the second qualification criterion is met, and the matching of the medium flow limiting hole is completed.

11. The aircraft fuel tank inerting system flow restriction hole matching test method according to claim 10, characterized in that: In step S10.2, the process of adjusting the size of the medium flow limiting hole specifically includes: S10.2.

1. If the oxygen concentration of the nitrogen-rich gas in the medium flow mode is higher than O2+0.3%, reduce the size of the medium flow limiting orifice; S10.2.

2. If the oxygen concentration of the nitrogen-rich gas in the medium flow mode is lower than O2-0.3%, increase the size of the medium flow limiting orifice.

12. The aircraft fuel tank inerting system flow restriction hole matching test method according to claim 11, characterized in that: The matching process of large flow limiting holes is as follows: S11, setting the wheel load to air, and simulating the aircraft to climb and descend according to the designed profile; S12. Before the aircraft descends, the inlet pressure of the air separation device is adjusted to a third pressure, where the third pressure is the average bleed air pressure during the aircraft's descent phase; S13, during the descent phase, the aircraft fuel tank inerting system enters the high flow mode; S14, after the inlet pressure is stabilized, record the minimum pressure of the fuel tank in the large flow mode, as well as the nitrogen-rich gas flow and oxygen concentration at the outlet of the air separation unit; S15, comparing the minimum pressure of the fuel tank in the large flow mode with the third qualification criterion, if the third qualification criterion is not met, executing the following steps: S15.

1. Turn off the aircraft fuel tank inerting system; S15.

2. Adjust the size of the high flow restrictor orifice and reinstall the aircraft fuel tank inerting system; S15.

3. Start the aircraft fuel tank inerting system and introduce high-temperature or normal-temperature gas into the aircraft fuel tank inerting system through the gas source to preheat the air separation device; S15.4, after the air separation device is fully preheated, return to step S11; Repeat steps S11-S15 until the third qualification criterion is met, and then proceed to step S16; S16, determining whether the gas introduced by the gas source to the aircraft fuel tank inerting system in the large flow mode is high temperature gas, if so, proceeding to step S17, if not, executing the following steps: S16.

1. Turn off the aircraft fuel tank inerting system; S16.

2. Start the aircraft fuel tank inerting system and introduce high-temperature or normal-temperature gas into the aircraft fuel tank inerting system through the gas source to preheat the air separation device; S16.3, after the air separation device is fully preheated, return to step S11; S17. Turn off the aircraft fuel tank inerting system and complete the matching of the large flow limiting orifice.

13. The aircraft fuel tank inerting system flow restriction hole matching test method according to claim 12, characterized in that: In step S15.2, the process of adjusting the size of the large flow limiting hole specifically includes: S15.2.

1. If the minimum pressure of the fuel tank in the high flow mode during the descent phase is less than P min kPa, increase the size of the large flow limiting hole; S15.2.

2. If the minimum pressure of the fuel tank in the high flow mode during the descent phase is greater than (P min +2) kPa, reduce the size of the large flow limiting hole.

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