Improved method for diagnosing pollution in an aircraft tank

Abstract

Improved method for diagnosing pollution of an aircraft tank The invention relates to a method for diagnosing pollution of an aircraft tank (10) comprising a flexible bladder (12) housed in a chamber (14) provided in a structure of said aircraft, and an absorbent material (21) provided between said bladder (12) and said chamber (14), the chamber (14) comprising at least one drainage outlet (22), characterized in that it consists of diagnosing fuel pollution in the chamber (14) by implementing the following steps: pressurizing said chamber (14) to a predetermined pressure; purging the air contained in the chamber (14); separating the liquid fuel from the air laden with fuel vapor; analyzing the air laden with fuel vapor to determine a pollution level. Abstract figure: Fig.2

Description

Title of the invention: Improved method for diagnosing pollution in an aircraft tank

[0001] The present invention relates to a method for diagnosing pollution in an aircraft tank, in particular a method particularly suitable for rapidly determining a level of fuel pollution in an aircraft tank.

[0002] Determining the level of pollution caused by a leak from an aircraft tank requires a good knowledge of the structure of the aircraft. Both from the outside and from the inside of the aircraft, certain current methods of determining the level of pollution require as much skill as the repair operations of said tanks.

[0003] Some aircraft tanks may be in the form of a flexible bladder made of rubber, neoprene, or other material, arranged in a cavity in the structure of the aircraft or in a part of the aircraft, inside the wings or in the hold for example.

[0004] In order to evacuate any leakage, the structure containing said flexible reservoir is generally provided with at least one drainage inlet. Said structure also comprises an air inlet to compensate for the consumption and the reduction in volume of the bladder. Furthermore, the flexible bladder is surrounded by an absorbent material generally made of polymer foam or similar.

[0005] In this way, when a fuel leak occurs at the bladder, the flow circulates in the absorbent material disposed in the interstitial space 20 between said bladder and the structure up to the level of the outlet of the drainage socket, where said leak flow is easily identifiable.

[0006] If the leak is detected, it remains very difficult to determine and carry out the diagnosis necessary for decontamination without removing the bladder from the structure of the aircraft. Thus, currently, the level of fuel retained by the absorbent material is difficult to quantify. In order to decontaminate an aircraft tank, it is necessary to completely extract said bladder from the structure of the aircraft and then remove the absorbent material from the tank for cleaning or replacement. This complete extraction requires disassembly and reassembly of all the internal connections with the bladder. Indeed, the bladder includes numerous fluid connections and numerous mechanical connections in order to be held in place. These are therefore long and tedious operations affecting the operational availability of the aircraft and considerably increasing the cost of maintenance operations.

[0007] Furthermore, when it is extracted or replaced in the structure of the aircraft, said flexible bladder is subjected to mechanical stresses likely to damage it. Usually, simply removing the bladder or absorbent material damages them and they need to be replaced, leading to much higher maintenance costs.

[0008] The invention aims to overcome at least one of the drawbacks cited by proposing to simplify the diagnosis of pollution of an aircraft tank.

[0009] To this end, the invention relates to a method for diagnosing pollution of an aircraft tank comprising a flexible bladder housed in a chamber provided in a structure of said aircraft, and an absorbent material provided between said bladder and said chamber, the chamber comprising at least one drainage outlet, remarkable in that it consists of diagnosing fuel pollution in the chamber by implementing the following steps:

[0010] from the drainage outlet, pressurize said chamber to a predetermined pressure;

[0011] from the drainage outlet, purge the air contained in the chamber;

[0012] using a fuel separator, separating the liquid fuel from the air laden with fuel vapor;

[0013] using a pollution diagnostic device, analyzing the air laden with fuel vapor to determine a pollution level.

[0014] The diagnostic method of the invention thus makes it possible to extract the purged air contained therein from the tank in order to determine the level of pollution. It will be noted that the fuel separator advantageously makes it possible to filter the liquid fuel from the purged air loaded with fuel particles, for the purpose of better analysis.

[0015] According to one embodiment of the invention, the pollution level is detected using an infrared fuel sensor.

[0016] According to one embodiment of the invention, the air loaded with fuel vapor is purged by the Venturi effect for the purpose of its analysis.

[0017] According to one embodiment of the invention, the steps of the method are repeated a predetermined number of cycles, preferably five, the pollution level corresponding to an average of the pollution levels measured.

[0018] According to one embodiment of the invention, prior to the step of pressurizing said chamber, a check is carried out on the structural state of the tank comprising the following steps consisting of:

[0019] - from the drainage outlet, pressurize said chamber to a predetermined pressure finished;

[0020] - using a pressure sensor, measure the pressure in said chamber to determine a variation representative of an air leak in the tank.

[0021] The predetermined pressure for monitoring the structural condition of the tank is preferably less than or equal to 10 mbar.

[0022] According to one embodiment of the invention, the control of the structural state of the tank comprises the following steps consisting of:

[0023] - from the drainage outlet, purge the air contained in the chamber until reaching a pressure in said chamber reduced by the predetermined pressure;

[0024] - compare the resulting pressure in the chamber to a threshold pressure value, pre potentially zero, to identify a leak in the tank.

[0025] According to another aspect, the invention relates to a system for diagnosing pollution of an aircraft tank capable of implementing the pollution diagnosis method as defined above, the pollution diagnosis system being remarkable in that it comprises:

[0026] - a fuel separator configured to be fluidically connected to a fuel intake aircraft tank drainage;

[0027] - a fuel pollution diagnostic device configured to be connected flu specifically to the fuel separator.

[0028] Other characteristics and advantages of the invention will appear on reading the following non-limiting description.

[0029] [Fig.l] represents a schematic view of an aircraft tank equipped with a flexible bladder.

[0030] [Fig.2] represents a perspective view of the pollution diagnostic system according to the invention implementing the method of the invention.

[0031] As shown in [Fig.l], an aircraft tank 10 comprising a flexible bladder 12 housed in a chamber 14 provided in a structure of an aircraft. The flexible bladder 12 is intended to store fuel, here kerosene, for the needs of the aircraft.

[0032] Said flexible bladder 12 is held in the chamber 14 by several connections connecting it to the structure of the aircraft, an interstitial space 20 being provided between said bladder 12 and said chamber 14. This interstitial space 20 comprises an absorbent material 21 surrounding the flexible bladder 12 to allow the absorption of fuel that may escape from the bladder 12. The chamber 14 comprises at least one drainage outlet 22 allowing the evacuation of any fuel C flows that may escape from the bladder 12.

[0033] The chamber 14 forms a substantially closed volume whose sealing depends mainly on the sealing of the structure of the aircraft.

[0034] A chamber 14 may be located in different parts of the structure of the aircraft, such as for example inside a wing or a hold, and it comprises at least one access opening 24 closed by an inspection hatch 27 for carrying out various checks and repairs, in particular during maintenance operations.

[0035] Referring to [Fig.2], there is shown a cutaway view of the reservoir 10 of a aircraft connected to a pollution diagnostic system of an aircraft tank 10, comprising a fuel separator 26 fluidly connected to the drainage socket 22 of the aircraft tank 10 and a pollution diagnostic device 28 comprising a fuel pollution analyzer and fluidly connected to the fuel separator 26.

[0036] The method for diagnosing pollution of an aircraft tank 10 according to the invention will now be described according to a preferred embodiment.

[0037] In order to enable the pollution diagnosis of the tank 10 without extraction of the flexible bladder 12 and the absorbent material 21 from the structure of the aircraft, the pollution diagnosis method according to the invention implements the following steps in an automated manner:

[0038] pressurize said chamber 14 to a predetermined pressure;

[0039] purge the air contained in chamber 14;

[0040] separating the liquid fuel from the air loaded with fuel vapor;

[0041] analyze the air loaded with fuel vapor to determine a pollution level.

[0042] The access opening 24 of the chamber 14 is closed during the operation of tank 10 pollution diagnosis.

[0043] The predetermined pressure of the chamber 14 corresponds to the maximum pressure that the bladder 12 can withstand, for example 10 mbar in the case of the chamber 14.

[0044] The injection of air in order to pressurize the chamber 14 is carried out by the drainage port 22 giving access to the interstitial space 20 comprising the absorbent material 21 arranged between the bladder 12 and the chamber 14. The air injected by the drainage port 22 is advantageously supplied by an air compressor supplying the diagnostic device 28 itself connected to the fuel separator 26. Thus, the air supplied by the compressor first passes through the diagnostic device 28, then through the fuel separator 26 before reaching the drainage port 22 and pressurizing the chamber 14.

[0045] Once the pressurization of the chamber 14 has been reached, the air contained in the chamber 14 can be purged from it via the same drainage inlet 22. For this purpose, the fuel separator 26 is equipped with suction means allowing the suction of the air contained in the interstitial space 20 by Venturi effect. The chamber 14 is then gradually emptied of its air.

[0046] It will be understood that the air purged in the chamber corresponds to the air contained in the interstitial space, of course in the case where the bladder does not include a defect which could make it permeable to gases.

[0047] A proportion of the liquid fuel that can be retained by the absorbent material 21 in the chamber 14 and the air laden with fuel vapor are then extracted from the chamber 14 to pass to the separator 26 where they are separated. The liquid fuel is retained in a tank 10 of the separator 26 provided for its storage. The air purged from the chamber 14 filtered of liquid fuel and laden with fuel vapor is then directed to the diagnostic device 28 for analysis.

[0048] For this purpose, the diagnostic device 28 comprises a fuel pollution analyzer capable of determining the content of polluting particles (ppm) contained in the air to be analyzed.

[0049] The fuel pollution analyzer is advantageously formed by an infrared fuel sensor capable of measuring the pollution rate of the air it receives.

[0050] After analysis, the air loaded with fuel vapor can be discharged through an exhaust outlet of the pollution diagnostic device 28.

[0051] In order to determine a more precise pollution level, the method of the invention can be repeated automatically. An average of the pollution levels measured at each of the cycles is then calculated.

[0052] In order to optimize the maintenance operation time, it is also planned to check the structural state of the tank 10 formed in the structure of the aircraft. To this end, prior to the step of pressurizing said chamber 14, a check of the structural state of the tank 10 is advantageously carried out by automatically carrying out the following steps consisting of:

[0053] - pressurize said chamber 14 to a predetermined pressure;

[0054] - measuring the pressure in said chamber 14 to determine a variation represented indicating an air leak in the tank 10.

[0055] The pressurization of the chamber 14 is carried out by the same method described previously where the predetermined pressure is preferably less than or equal to 10 mbar.

[0056] The pressure measurement is carried out using a pressure sensor provided to measure the pressure in the chamber 14.

[0057] A variation in the pressure in the chamber 14 is then representative of an air leak from the tank 10. In this case, the pollution diagnostic operation cannot be carried out optimally. The operator warns of a defect in the structure of the tank 10 and saves himself an unsuccessful and distorted diagnostic operation.

[0058] In addition, the following steps may be additionally provided to confirm a defect in the structure of the tank 10, namely the following steps:

[0059] - purge the air contained in the chamber 14 until a pressure is reached in said chamber 14 reduced by the predetermined pressure;

[0060] - compare the resulting pressure in chamber 14 to a threshold pressure value to identify an air leak in the tank 10.

[0061] Here again, the air is purged from the drainage outlet 22 via the separator 26.

[0062] Once the air has been purged, the resulting pressure in the chamber 14 is measured using the same pressure sensor. The pressure thus measured is compared to a predetermined value corresponding to zero or globally zero pressure.

[0063] An air leak from the reservoir 10 can be identified when the resulting pressure of the chamber 14 is substantially different from the predetermined value.

[0064] It can therefore be seen that the method for checking the structural condition of the tank 10 which has just been described allows the pollution diagnosis method according to the invention to identify an air leak in the tank 10 of the aircraft without dismantling the flexible bladder 12 and the absorbent material 21. Advantageously compared to the methods of the prior art, said pollution diagnosis method and method for checking the structural condition of the tank 10 can be carried out in just a few hours, which has a significant impact on the availability of the aircraft.

[0065] Generally, particularly on combat aircraft, the space available in the structure of the aircraft is used to the maximum and consequently, accessibility to the interior of the structure of the aircraft is limited to components requiring regular maintenance. By allowing a pollution diagnosis without disassembly, the method according to the invention is likely to allow a simplification of the design of the structure of the aircraft at the level of the chamber(s) provided to receive a tank bladder by limiting the number of accesses necessary for maintenance of the aircraft.

[0066] The invention also covers the application of the present diagnostic method to other reservoirs or devices comprising a flexible bladder housed in a volume similar to a chamber.

[0067] Obviously, the invention is not limited to the examples which have just been described and numerous adjustments can be made to these examples without departing from the scope of the invention. In particular, the different characteristics, forms, variants and embodiments of the invention can be associated with each other in various combinations insofar as they are not incompatible or exclusive of each other. In particular, all the variants and embodiments described above can be combined with each other.

Claims

Claims

1. Method for diagnosing pollution of an aircraft tank (10) comprising a flexible bladder (12) housed in a chamber (14) formed in a structure of said aircraft, and an absorbent material (21) provided between said bladder (12) and said chamber (14), the chamber (14) comprising at least one drainage inlet (22), characterized in that it consists of diagnosing fuel pollution in the chamber (14) by implementing the following steps: from the drainage inlet (22), pressurizing said chamber (14) to a predetermined pressure; from the drainage inlet (22), purging the air contained in the chamber (14); using a fuel separator (26), separating the liquid fuel from the air loaded with fuel vapor; using a pollution diagnostic device (28), analyzing the air loaded with fuel vapor to determine a pollution level.

2. Pollution diagnostic method according to the preceding claim, characterized in that the pollution level is detected using an infrared fuel sensor.

3. Pollution diagnosis method according to any one of the preceding claims, characterized in that the air loaded with fuel vapor is purged by the Venturi effect for the purpose of its analysis.

4. Pollution diagnosis method according to any one of the preceding claims, characterized in that the steps of the method are repeated a predetermined number of cycles, preferably five, the pollution level corresponding to an average of the pollution levels measured.

5. Pollution diagnosis method according to any one of the preceding claims, characterized in that, prior to the step of pressurizing said chamber (14), a check is carried out on the structural state of the tank (10) comprising the following steps consisting of: from the drainage inlet (22), pressurizing said chamber (14) to a predetermined pressure; - using a pressure sensor, measuring the pressure in said chamber (14) to determine a variation representative of an air leak in the tank (10).

6. Pollution diagnosis method according to the preceding claim, characterized in that the control of the structural state of the tank (10) comprises the following steps consisting of: - from the drainage outlet (22), purge the air contained in the chamber (14) until a pressure in said chamber (14) reduced by the predetermined pressure is reached; - comparing the resulting pressure in the chamber (14) to a threshold pressure value, preferably zero, to identify an air leak in the tank (10).

7. A pollution diagnostic system for an aircraft tank (10) comprising a flexible bladder (12) housed in a chamber (14) provided in a structure of said aircraft, and an absorbent material (21) provided between said bladder (12) and said chamber (14), the chamber (14) comprising at least one drainage inlet (22), wherein said pollution diagnostic system is capable of implementing the pollution diagnostic method according to any one of the preceding claims and comprises: - a fuel separator (26) configured to be fluidically connected to a drainage outlet (22) of the aircraft tank (10), and equipped with suction means shaped to purge the air contained in the chamber (14), said fuel separator (26) being shaped to separate the liquid fuel from the air loaded with fuel vapor; - a pollution diagnostic device (28) fluidly connected to the fuel separator (26) and comprising a fuel pollution analyzer configured to analyze the air laden with fuel vapor to determine a pollution level; and - an air compressor supplying the diagnostic device (28) to pressurize the chamber (14).

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