TANK AND SENSOR ARRANGEMENT FOR DETERMINING THE LIQUID LEVEL OF AN AIRCRAFT TANK, METHOD FOR USE OF SUCH A SENSOR

Description

DOMAINE TECHNIQUE

[0001] The present invention relates to the field of measuring a liquid level in a tank of an aircraft, in particular, an oil tank of a helicopter.

[0002] It is known to use a submerged level sensor in an aircraft tank to measure a liquid level, for example, by measuring the position of a float of the level sensor in the tank. A submerged level sensor needs to adapt to the shape of the tank, which is a significant disadvantage given that tanks are generally of different shapes depending on the aircraft. In addition, a submerged level sensor has the disadvantage of being difficult to access, which penalizes maintenance.

[0003] As is known, a tank comprises a liquid phase, the level of which is variable, and a complementary gas phase. It has been proposed to use a differential type level sensor to determine the liquid level in a tank by measuring, on the one hand, the pressure of the liquid phase and, on the other hand, the pressure of the gas phase.

[0004] In practice, with reference to the figure 1 , a differential type level sensor 9 comprises a first tubing 91 in relation to the liquid phase PL and a second tubing 92 in relation to the gas phase PG of a tank 100. The level sensor 9 determines from the pressure difference a liquid level NL which is transmitted to a computer 6 of the aircraft in order to provide liquid level information to the propulsion system of the aircraft or to the pilot.

[0005] Such tubings 91, 92 extend externally to the tank 91, 92, which increases the bulk. In addition, it is necessary to provide dedicated openings in the tank 100 to allow the tubings 91, 92 to pass through, which complicates the manufacture of the tank 100. These problems are all the more significant since each tank 100 comprises several differential level sensors 9 in order to ensure consolidation of the level measurement and limit errors, in particular, linked to movements of the aircraft. During maintenance, it is necessary to remove the tubings 91, 92, which is complex and time-consuming.

[0006] The invention thus aims to eliminate at least some of these drawbacks by proposing a liquid level determination sensor which adapts to any tank, the maintenance of which is simplified while having limited space requirements.

[0007] A system for measuring the quantity of fuel in an aircraft tank is known in the prior art from patent application EP2700913A1. PRESENTATION DE L'INVENTION

[0008] The invention relates to an assembly according to claim 1.

[0009] The invention advantageously provides a two-part sensor that allows the orifice to be conveniently closed to prevent any loss of liquid and / or pollution. In addition, a removable assembly allows for simple and rapid maintenance of the measuring element. This can thus be inspected and / or replaced without difficulty.

[0010] According to one aspect of the invention, the measuring device comprises an external pipe opening outside the tank to measure the external pressure as a reference pressure. Thus, the measuring device makes it possible to use the external pressure as a reference pressure. This makes it possible to form a sensor with reduced bulk. It is therefore not necessary to provide a high opening in the tank.

[0011] According to another aspect of the invention, the measuring device comprises a gas line configured to be in fluid communication with a gas phase of the tank as a reference pressure. Preferably, the gas line is connected to a filler cap of the tank, which makes it possible to avoid forming a dedicated orifice in the tank. According to an example not forming part of the invention as claimed, the gas line is flexible so as to allow convenient manipulation of the filler cap with the gas line.

[0012] Preferably, the measuring device comprises two pressure measuring members in order to ensure redundancy and / or consolidation of the liquid level measurement.

[0013] Preferably, the assembly comprises a single sensor.

[0014] Preferably, the reservoir having a minimum liquid height designated "alert height", the orifice is positioned at a height lower than said alert height. Thus, the liquid line is always filled with liquid to provide liquid pressure.

[0015] Preferably, the orifice is a drain orifice of the tank in which a drain plug is mounted, the sensor is integrated into said drain plug.

[0016] A measurement at the drain plug is very advantageous since the closing device fulfills a sealing function without requiring dedicated machining in the tank. En In addition, the position of the drain plug in a very low position ensures that the liquid line will always be filled with liquid to provide liquid pressure. An integration of the sensor in the drain plug allows the invention to be applied to circulating aircraft tanks (backward compatibility), which is very advantageous.

[0017] The reservoir comprises a mouth formed around the orifice, the mouth comprising at least one opening, in fluid communication with a gas phase of the reservoir via a first portion of internal gas conduit, the closure device comprising a second portion of internal gas conduit configured to supply the measuring member with the gas pressure.

[0018] An internal gas line significantly reduces the size, the closure device allowing the measuring device to be supplied with liquid pressure and gas pressure. The size is reduced as well as the mass. Preferably, the automatic closing member of the liquid line allows the liquid line and the second portion of internal gas line to be closed when the measuring device is not mounted on the closure device.

[0019] Preferably, the assembly comprises at least one auxiliary pressure sensor configured to measure a liquid pressure at a determined height of the orifice so as to deduce a liquid density therefrom. By knowing the density, the type of liquid can be deduced to determine a liquid level correction parameter. Thus, the liquid level supplied to the pilot is very precise.

[0020] The invention further relates to an aircraft comprising a sensor as presented previously and / or an assembly of an aircraft tank and a sensor as presented previously.

[0021] The invention also relates to a method of using a sensor mounted in an aircraft tank, the sensor closure device being mounted in the orifice of the tank, the closure member closing the liquid line, the method comprising steps consisting of: Mount the measuring device on the closing device so as to put the measuring member into fluid communication with the liquid pressure, the closing member being inactivated following the mounting, Measure a pressure difference between, on the one hand, the liquid pressure in the liquid pipe and, on the other hand, a reference pressure so as to deduce the liquid level in the tank.

[0022] Preferably, the method includes a step of issuing an alarm when the liquid pressure is equal to the reference pressure. Thus, under extreme conditions (rapid descent / rise), the operator is informed that the level measurement is not reliable. He can thus control by taking into account only the other relevant measurements. PRESENTATION DES FIGURES

[0023] The invention will be better understood upon reading the following description, given by way of example, and referring to the following figures, given by way of non-limiting examples, in which identical references are given to similar objects. There figure 1 is a schematic representation of a tank with a differential measuring sensor according to the prior art. The [ Fig.2 ] is a schematic representation of a tank with a sensor according to a first embodiment not forming part of the invention as claimed. The [ Fig.3 ] is a close-up schematic representation of the sensor of the [ Fig.2 ]. There [ Fig.4 ] is a schematic representation of a tank with a sensor according to a second embodiment not forming part of the invention as claimed. The [ Fig.5 ] is a schematic representation of a tank with a sensor according to one embodiment of the invention. The [ Fig.6 ], there [ Fig.7 ] and the [ Fig.8 ] are schematic representations of the integration of two measuring devices in a sensor. The [ Fig.9 ] is a schematic representation of using an auxiliary sensor to determine liquid density.

[0024] It should be noted that the figures set out the invention in detail to implement the invention, said figures can of course be used to better define the invention if necessary. DESCRIPTION DETAILLEE DE L'INVENTION

[0025] The invention will be presented for an oil tank of a helicopter but it goes without saying that the invention applies to other types of tank (fuel, coolant, etc.) and to other types of aircraft (airplane, etc.).

[0026] With reference to the [ Fig.2 ], a tank 100 of a helicopter is schematically represented. The tank 100 is represented in the form of a block but this is generally complex with a non-flat bottom. The tank 100 comprises a liquid phase PL, the level of which is variable, and a complementary gaseous phase PG. The interface between the two phases PL, PG corresponds to the liquid level NL to be determined.

[0027] In this example, the tank 100 has a wall 102 having a thickness enabling it to withstand pressure, generally metallic. The tank 100 has at least one liquid inlet H1 and one liquid outlet H2 in order to supply a liquid circuit, in particular, an oil circuit for cooling components of an aircraft turbomachine.

[0028] In this example not forming part of the invention as claimed, the tank 100 comprises a drain orifice 101 which is positioned in a low point of the tank 100 so as to allow its draining by gravity. Such a drain orifice 101 is formed during the manufacture of a tank 100 and advantageously does not require additional machining.

[0029] As illustrated in [ Fig.3 ], the drain orifice 101 comprises a mouth, preferably cylindrical, to cooperate with a drain plug closing said drain orifice 101. In this example, a sensor 1 for determining a liquid level NL is integrated into said drain plug so that the latter advantageously fulfills a dual function and limits the size.

[0030] It nevertheless goes without saying that the sensor 1 could be used independently, in particular, in a fluid circulation orifice other than the drain orifice 101.

[0031] Preferably, the sensor 1 is positioned at a height lower than a minimum liquid height designated “alert height” HA. Thus, the sensor 1 is always immersed and subjected to the liquid pressure as will be presented later. The drain orifice 101 has a very low height and meets this condition. Preferably, the sensor 1 is located in a position that is not very subject to turbulence due to the suction and discharge of liquid (proximity to the liquid inlet H1 and the liquid outlet H2). The drain orifice 101 is generally located opposite and meets this condition.

[0032] When an aircraft turbomachine is started, a certain quantity of oil is taken to fill the turbomachine pipes (the "gulping" phenomenon). The HA warning height advantageously takes this phenomenon into account. Liquid level determination sensor

[0033] With reference to the [ Fig.3 ], the sensor 1 comprises a closing device 2, configured to be mounted in the drain orifice 101, and a measuring device 3, removably mounted on the closing device 2. In other words, the measuring device 3 forms a removable accessory which is not necessary to close the tank 100. Due to its removable nature, the maintenance of the measuring device 3 is greatly simplified.

[0034] The closure device 2 comprises a liquid pipe 20 configured to conduct liquid from the drain orifice 101 and an automatic closure member 21 of the liquid pipe 20 if the measuring device 3 is not mounted on the closure device 2. As will be presented later, the cooperation of the measuring device 3 with the closure device 2 makes it possible to inactivate the automatic closure member 21 and allows a circulation of liquid making it possible to measure the liquid pressure P2. The automatic closure member 21 can be in various forms, in particular, a non-return valve.

[0035] Thus, the closing device 2 advantageously fulfills a plug function by plugging the drain orifice 101. The measuring device 3 makes it possible to measure the liquid level NL and can be replaced quickly in the event of a malfunction. This solution is advantageous since it can be transposed to any existing tank 100. In addition, in the event of maintenance or technological development of the measuring device 3, it can be replaced in a practical manner.

[0036] Preferably, the closing device 2 and the measuring device 3 are mounted together mechanically, for example, by screwing, by fitting, by a bayonet system or the like. It goes without saying that a magnetic mounting could also be suitable.

[0037] According to one aspect of the invention, to allow emptying, a pipe is inserted from the outside into the automatic closing member 21 in order to inactivate it and allow the liquid to flow. Alternatively, with reference to the [ Fig.3 ], the closing device 2 could comprise a control lever 22 configured to deactivate the automatic closing member 21 and allow emptying of the tank 100.

[0038] According to the invention, the measuring device 3 comprises at least one pressure measuring member 30 configured to measure a pressure difference between, on the one hand, the liquid pressure P1 in the liquid pipe 20 and, on the other hand, a reference pressure so as to deduce therefrom the liquid level NL in the reservoir 100. As will be presented subsequently, the reference pressure can be of different nature.

[0039] The measuring member 30 is connected to a computer 6 of the aircraft in order to provide liquid level information to the propulsion system of the aircraft or to the pilot.

[0040] Preferably, the pressure measuring member 30 is in the form of an electronic chip configured to determine a pressure difference between the liquid pressure P1 and the reference pressure.

[0041] In this example not forming part of the invention as claimed, with reference to the [ Fig.3 ], the measuring device 3 comprises a single pressure measuring member 30. The measuring device 3 comprises an external pipe 31, opening outside the tank 100. In other words, the reference pressure is the external pressure Pext of the external environment Mext, that is to say, atmospheric pressure. The atmospheric pressure Pext forms a stable reference pressure which makes it possible to precisely determine the liquid level NL in a differential manner.

[0042] Thus, the integration of a sensor 1 in a drain plug makes it possible to measure the liquid level NL without modifying the reservoir 100, which is advantageous. The space requirement is also limited.

[0043] According to an example not forming part of the invention as claimed, with reference to the [ Fig.4 ], the measuring device 3 comprises a gas pipe 32 in fluid communication with the gas phase PG of the reservoir 100. In other words, the reference pressure Pref is the gas pressure P2, that is to say, the pressure of the gas phase PG. With reference to the [ Fig.4 ], the gas line 32 extends externally to the tank 100 and connects the measuring member 30 to an upper opening 103 formed in the tank 100. The gas line 32 may be flexible or rigid. Preferably, the gas line 32 is equipped with pneumatic connections at its ends.

[0044] According to this example, the gas line 32 opens into a filler cap (not shown) mounted in a filler orifice located in the upper part of the tank 100. The use of a gas line 32 which is flexible makes it possible to avoid its disassembly when the tank 100 is filled. The filler cap can thus be handled while remaining connected to the gas line 32. The gas phase PG makes it possible to form a relevant comparison basis for determining the liquid level NL.

[0045] According to the invention, with reference to the [ Fig.5 ], the gas pipe 32' extends internally to the reservoir 100 and to the closure device 2 and makes it possible to connect a high orifice 104 (tapping) opening into the interior of the reservoir 100 and the measuring member 30 of the measuring device 3. The internal gas pipe 32' comprises a first portion 32a' which is formed in the thickness of the wall 102 of the reservoir 100 and a second portion 32b' which is formed in the closure device 2. Preferably, the mouth 101 of the reservoir 100 comprises an opening which allows fluid communication between the two portions 32a', 32b'. Preferably, seals are provided to ensure sealing, in particular, O-rings.

[0046] In other words, the closing device 2 makes it possible to supply a liquid pressure P1 and a gas pressure P2 in a centralized and practical manner to the measuring device 3. The measuring member 30 thus makes it possible to deduce the liquid level NL.

[0047] Preferably, the first portion 32a' of the gas pipe 32' extends upwards from the upper orifice 104 and downwards from the opening which allows fluid communication between the two portions 32a', 32b, to avoid any phenomenon of accumulation of liquid mist in the gas pipe 32', which would distort the measurement.

[0048] According to a preferred aspect, with reference to the figures 6 à 8 , the measuring device 3 of the sensor 1 comprises two measuring members 30a, 30b in order to carry out independent level measurements NL1, NL2 which are supplied to the computer 6. This advantageously makes it possible to detect early any defect in one of the measuring members 30a, 30b. Advantageously, the measuring members 30a, 30b are integrated into the same sensor 1 to reduce the size and the number of machining operations in the tank 100. Preferably, each tank 100 is associated with only one sensor 1, which may comprise one or more measuring members 30a, 30b. Due to the redundancy, it is no longer necessary to provide a window in the tank 100 in order to allow a visual check of the liquid level NL.

[0049] As illustrated in [ Fig.6 ], the two measuring members 30a, 30b each make it possible to measure a fluid pressure P1 and an external pressure Pext. In this example, the two measuring members 30a, 30b are supplied separately in order to guarantee the independence of the measurements. Nevertheless, it goes without saying that communication with the liquid phase PL or the external environment Mext could be common in order to limit the size.

[0050] With reference to the [ Fig.7 ], the two measuring members 30a, 30b each make it possible to measure a fluid pressure P1 and a gas pressure P2. In this example, the two measuring members 30a, 30b are supplied separately in order to guarantee the independence of the measurements. Nevertheless, it goes without saying that communication with the liquid phase PL or the gas phase PG could be common in order to limit the size.

[0051] With reference to the [ Fig.8 ], the first measuring member 30a makes it possible to measure a fluid pressure P1 and a gas pressure P2 while the second measuring member 30b makes it possible to measure a fluid pressure P1 and an external pressure Pext. The use of two reference pressures of different natures makes it possible to obtain two level measurements NL1, NL2 which are independent and decorrelated. This makes it possible to detect a drift of one of the measuring members 30a, 30b or another fault in a practical manner. Indeed, when the turbomachine is stopped, the pressures P2 and Pext must be identical and lead to the same liquid level measurement NL1, NL2.

[0052] The computer 6 can thus consolidate the measurements of level NL1, NL2 (average, etc.) in order to provide qualitative information to the aircraft propulsion system or to the pilot.

[0053] Optionally, the density of the liquid (here the oil density) is also determined. This information is important since the same turbomachine can be used with oils of different types. By knowing the type of oil, a correction parameter ΔNL1 for the NL level measurement can be determined and thus the measurement accuracy improved.

[0054] With reference to the [ Fig.9 ], an auxiliary pressure sensor 4 is placed in fluid communication with the liquid phase via an upper opening 104 of the reservoir 100 and with the external environment Mext having an external pressure Pext in order to carry out a differential pressure measurement which is supplied to the computer 6. Given that the vertical distance h between the upper opening 104 and the orifice 101 is known, the density of the liquid ρ can advantageously be deduced from it by the following formula: ρ = P 3 − P 2 gh * cos α

[0055] With g the gravity and α the angle formed between the vertical of the aircraft and the axis of gravity.

[0056] Preferably, the density measurement ρ is carried out after filling the tank 100. The density measurement ρ is stored in the computer 6 and will be used to determine the correction parameter ΔNL1 of the level measurement NL. It goes without saying that the density measurement ρ could be determined more frequently.

[0057] It is also possible to correct the filling level NL as a function of temperature. For this purpose, an independent measurement of the liquid temperature is taken and supplied to the computer 6 and will be used to determine a correction parameter ΔNL2 of the level measurement NL.

[0058] Thus, we obtain a corrected level measurement NL* according to the following formula: NL * = NL + ΔNL 1 + ΔNL 2

[0059] Optionally, the measuring device 3 comprises an amplification member, in particular a hydraulic one, in order to increase its sensitivity to the liquid pressure P1 and to accurately measure any variation. For example, the amplification member is in the form of a piston rod whose ends have different sections so as to amplify the variations.

[0060] Optionally, the closing device 2 comprises a strainer in order to filter impurities in the liquid, in particular, in the automatic closing member 21. Method of use

[0061] The invention also relates to a method of using a sensor 1 mounted in a drain orifice 101 of an aircraft tank 100. The method of use will be presented in relation to the embodiment of the [ Fig. 5 ].

[0062] In this example of implementation, in the initial position, only the closing device 2 is mounted in the drain orifice 101. The closure member 21 is active and prevents any flow of liquid. If draining is desired, an operator can insert a pipe into the closure member 21 or act on the control lever 22.

[0063] To carry out a liquid level measurement NL, the operator mounts the measuring device 3 on the closing device 2, which puts the measuring member 30 into fluid communication with the liquid pipe 20 which has a liquid pressure P1. As illustrated in [ Fig.5 ], the pressure measuring member 30 is also in fluid communication with the gas phase PG which has a gas pressure P2. Advantageously, the closing device 2 directly allows this fluid communication.

[0064] The method comprises a step of determining the liquid level NL from the liquid pressure P1 and the gas pressure P2 measured by the measuring member 30. Such a differential measurement is robust.

[0065] By integrating the sensor 1 into a drain plug, liquid level measurement can be conveniently implemented on any type of tank 100. The two-part structure of the sensor 1 allows for draining when necessary while facilitating maintenance since the measuring device 3 can be removed in a removable manner.

[0066] The invention also relates to a method for detecting operating conditions from the sensor 1 according to the invention, in particular, extreme conditions such as a rapid climb / descent of the aircraft (abrupt change in altitude).

[0067] Indeed, during a rapid ascent / descent of the aircraft, the liquid housed in the tank 100 is subjected to the forces of gravity, which modifies the pressures measured by the sensor 1.

[0068] According to an example of measurement implemented, when the pressure difference is zero, the method comprises a step of issuing an alarm which is provided with the liquid level measurement NL or replaces it in order to inform the propulsion system or the pilot of the aircraft that the liquid level measurement NL is not reliable given the exceptional conditions. Thus, advantage is taken of the differential measurement to verify the operating conditions and deduce therefrom an index of relevance of the liquid level measurement NL which is provided.

Claims

1. Assembly of an aircraft tank (100) and a sensor (1) for determining a liquid level (NL) for an aircraft tank (100), the sensor (1) comprising: - a closure device (2), mounted in a port (101) of the tank (100) allowing liquid to circulate, and a measuring device (3), removably mounted on the closure device (2), - the closure device (2) comprising a liquid line (20) configured to conduct liquid from the port (101) of the tank (100) and a member (21) for automatically sealing the liquid line (20) if the measuring device (3) is not mounted on the closure device (2), - the measuring device (3) comprising at least one pressure measuring member (30) configured to measure a pressure difference between, on the one hand, a liquid pressure (P1) in the liquid line (20) and, on the other hand, a reference pressure (P2, Pext) so as to deduce therefrom the liquid level (NL) in the tank (100), - the tank (100) comprising a mouthpiece formed around the port (101), the mouthpiece comprising at least one opening, in fluidic communication with a gas phase (PG) of the tank (100) via a first internal gas line portion (32a') formed in a thickness (102) of the tank (100), the closure device (2) comprising a second internal gas line portion (32b') configured to supply the measuring member (30) with the gas pressure (P2) of the gas phase (PG) of the tank (100) as reference pressure.

2. Assembly according to claim 1, wherein the measuring device (3) comprises an external line (31) opening to the outside of the tank (100) to measure the external pressure (Pext) as reference pressure.

3. Assembly according to one of claims 1 to 2, wherein the measuring device (3) comprises two pressure measuring members (30a, 30b).

4. Assembly according to one of claims 1 to 3, wherein the tank (100) having a minimum liquid height designated as "alert height (HA)", the port (101) is positioned at a height lower than said alert height (HA).

5. Assembly according to one of claims 1 to 4, wherein the port being a drain port (101) of the tank (100) in which a drain plug is mounted, the sensor (1) is integrated into said drain plug.

6. Assembly according to one of claims 1 to 5, comprising at least one auxiliary pressure sensor (4) configured to measure a liquid pressure (P3) at a determined height (h) of the port (101) so as to deduce therefrom a liquid density (ρ).

7. Aircraft comprising an assembly according to one of claims 1 to 6.

8. Method of using an assembly of an aircraft sensor (1) and a tank (100) according to one of claims 1 to 6, the closure device (2) of the sensor (1) being mounted in the port (101) of the tank (100), the sealing member (21) sealing the liquid line (20), the method comprising steps consisting of: - Mounting the measuring device (3) on the closing device (2) so as to place the measuring member (30) in fluidic communication with the liquid pressure (P1), the sealing member (21) being inactivated following the mounting, - Measuring a pressure difference between, on the one hand, the liquid pressure (P1) in the liquid line (20) and, on the other hand, a reference pressure (P2, Pext) so as to deduce therefrom the liquid level (NL) in the tank (100).

9. Method of use according to claim 8, comprising a step of emitting an alarm when the liquid pressure (P1) is equal to the reference pressure (P2, Pext).