Fuel-in-oil detection device using gas phase analysis

Abstract

Turbomachine comprising a lubrication circuit (20) through which a lubricant (21) flows, the lubrication circuit (20) comprising a first instrumented resonator (30) connected to a control and measurement unit (70) arranged to provide a purity indicator for the lubricant (21). Aircraft equipped with such a turbomachine. Purity measurement method. Figure for the abstract: Figure 2

Description

Title of the invention: Device for detecting fuel in oil by gas phase analysis Technical field

[0001] The invention relates to the field of engine lubrication circuits and more particularly to the prevention of pollution of such circuits. STATE OF THE PRIOR ART

[0002] In aircraft the lubrication system is essential to ensure the proper functioning of the engines. However, the lubrication system can be contaminated by fuel, which can cause problems with engine performance and flight safety, particularly due to the risk of ignition. The detection of fuel in the lubrication system is therefore crucial to ensure the reliability and safety of aircraft.

[0003] Heat exchangers are used to transfer heat generated by engines from the lubrication system to the fuel system to preheat the fuel before it is injected into the engines. These heat exchangers between the lubrication system and the fuel system can leak, which can cause the lubrication system to become contaminated with fuel.

[0004] There are several fuel detection technologies in the lubrication system for aircraft, such as infrared absorption spectroscopy, Raman spectroscopy and electrical impedance analysis. These technologies are designed to detect the presence of fuel in different parts of the lubrication system, including filters, heat exchangers and lines. Fuel detection systems must be robust and reliable to operate under varying environmental conditions, such as high temperatures and pressures, as well as in environments with vibrations and shocks.

[0005] Since fuels and lubricants have similar chemical properties, it is difficult to clearly establish the presence of fuel in the oil for low concentrations of fuel in the lubricant. In view of the effects of the presence of fuel in the oil, even at very low concentrations, it is necessary to have a reliable and sensitive device. SUBJECT OF THE INVENTION

[0006] The invention aims to improve the sensitivity of fuel detection in a lubricant circuit. Statement of the invention

[0007] For this purpose, a turbomachine is provided comprising a lubrication circuit traversed by a lubricant, the lubrication circuit comprising a first instrumented resonator, connected to a control and measurement unit arranged to provide an indicator of the purity of the lubricant.

[0008] We then obtain a turbomachine equipped with a reliable and robust measuring device which analyses a particular parameter (displacement of sound in a fluid) which is little subject to external disturbances. The analysis is thus easier and can be carried out using robust and reliable sensors.

[0009] According to other particular, non-exclusive and optional embodiments of the invention: - the lubrication circuit includes an exciter connected to the control and measurement unit; - the lubrication circuit includes a lubricant temperature sensor connected to the control and measurement unit; - the lubrication circuit comprises a reference lubricant capsule having a reference purity state, the capsule being arranged so that the reference lubricant is at the same temperature as the lubricant, the capsule comprising a second instrumented resonator connected to the control and measurement unit; - the first resonator includes a piezoelectric microphone. - the first resonator comprises a cylindrical tube, one end of which is closed; - the control and measuring unit is arranged to detect the presence of fuel in the lubricant; - the control and measurement unit is arranged to emit an alarm when a value of the purity indicator shows a deviation relative to a reference value which is greater than a predetermined threshold;

[0010] The invention also relates to an aircraft comprising a turbomachine as described above as well as a method for measuring the purity of a lubricant in a turbomachine comprising the following steps: - measure a resonance frequency of the first resonator; - determine a deviation between the measured frequency and a reference value; - issue an alert when the deviation is greater than a predetermined threshold.

[0011] Other characteristics and advantages of the invention will appear on reading the following description of a particular non-limiting embodiment of the invention. Brief description of the drawings

[0012] Reference will be made to the attached figures, among which: [Fig.l] [Fig.l] is a schematic cross-sectional representation of a turbomachine; [Fig.2] [Fig.2] is a partial schematic plan view of a fuel circuit and a carburetion circuit according to a first embodiment of the invention; [Fig.3] [Fig.3] is a partial schematic plan view of a fuel circuit and a carburetion circuit according to a second embodiment of the invention; [Fig.4] [Fig.4] is a partial schematic plan view of a fuel circuit and a carburetion circuit according to a third embodiment of the invention.

[0013] DETAILED DESCRIPTION OF PARTICULAR EMBODIMENTS

[0014] In a turbomachine, here a turbojet marked 1 in [Fig.l], the air is admitted into an inlet sleeve 2 to pass through a fan comprising a series of rotating blades 3 before splitting into a central primary flow which circulates in a vein called a circulation vein of a primary air flow and a secondary flow surrounding the primary flow.

[0015] The primary flow is compressed by compressor stages 4 and 5 before reaching a combustion chamber 6, after which it expands by passing through turbines 7, before being evacuated, generating thrust. The secondary flow is propelled directly by the fan to generate the main thrust.

[0016] The compressor stages 4 and 5 comprise fixed distributors regularly spaced around a shaft 8 mounted for rotation around a longitudinal axis AX in a nacelle 9 surrounding the assembly. The blades of the compressor stages 4 and 5 and of the turbines 7 are integral in rotation with the shaft 8. The shaft 8 is mounted for rotation relative to the nacelle 9 using several bearings 10 lubricated with oil and which are confined in enclosures 11.

[0017] In the present text, the terms "inner" or "internal" and "outer" or "external" are used with reference to the position or orientation relative to the axis of rotation of the turbine of the turbojet engine 1. In the present text, the terms "upstream" and "downstream" are used with reference to the position or orientation of an element according to the direction of air flow in the turbojet engine 1. An axial direction, a radial direction which is orthogonal to the axial direction and a circumferential direction which is orthogonal to the axial and radial directions are also defined.

[0018] The turbojet 1 comprises a lubrication circuit 20 traversed by a lubricant 21 and a supply circuit 40 traversed by a fuel 4L. The lubrication circuit 20 comprises a reservoir 22 of lubricant 21. The lubrication circuit 20 comprises a pump 23 and is connected to a heat exchanger 50 to constitute the hot circuit. The supply circuit 40 is also connected to the exchanger 50 to constitute the cold circuit. The calories of the lubrication circuit 20 are thus transferred to the power supply circuit 40.

[0019] According to a first embodiment of the invention, an enclosure 24 is connected via a tapping 25 to a lubricant 21 pipe 26 which extends, here, between the exchanger 50 and the reservoir 22.

[0020] An instrumented resonator 30, here provided with a piezoelectric cell microphone 31, extends into the enclosure 24. The resonator 30 comprises, here, a straight cylindrical tube 32, one end 33 of which is closed. The piezoelectric cell 31 is fixed by gluing the end 33. A temperature sensor 35 also extends into the enclosure 24. The resonator 30 and the temperature sensor 35 are connected to a control and measurement unit 70.

[0021] In operation, the device of the invention follows the following steps. According to a first step, the unit 70 controls the sending of an electrical excitation pulse 60 to the piezoelectric cell 31. This causes a deformation of the tube 32. According to a second step, the unit 70 measures the voltage supplied by the cell 31 during the time necessary for the tube 32 to return to its initial shape. According to a third step, the unit 70 deduces from the measured voltage a resonance frequency of the resonator 30. This frequency being affected by the medium in which the resonator 30 is located (here the lubricant 21), the unit 70 deduces therefrom, after applying a correction dependent on the temperature measured by the sensor 35, a measured circulation speed of a sound in the lubricant 21.According to a fourth step, the unit 70 determines a difference between the measured circulation speed and a reference speed (here a speed V0 corresponding to the speed of movement of a sound in the lubricant when the latter is in a state of absolute purity). According to a final step, the unit 70 issues an alert when the calculated difference is greater than a predetermined threshold. The value of the predetermined threshold ideally corresponds to the difference observable when the lubricant 21 comprises a fuel rate 41 substantially equal to or greater than five percent of fuel 41 in the lubricant 21.

[0022] Elements identical or analogous to those previously described will bear a numerical reference identical to this in the following description of a second and a third embodiment of the invention.

[0023] According to a second embodiment shown in [Fig.3], the cell 31 is glued to an inner wall 24.1 of the enclosure 24. It is then the enclosure 24 which acts as a resonator. The measurement method remains identical to that described above.

[0024] According to a third embodiment shown in [Fig.4], the temperature sensor 35 is replaced by a capsule 80 of reference lubricant 81 which has a reference purity state - here a lubricant 21 which has a rate of 0.0% of 4L fuel. The capsule 80 comprises an envelope 82 which extends into the enclosure 24 and is arranged so that the reference lubricant 81 is at the same temperature as the lubricant 21. The capsule 80 comprises a second instrumented resonator 83 connected to the control and measurement unit 70.

[0025] In operation, the device of the invention follows the following steps. According to a first step, the unit 70 controls the sending of an electrical excitation pulse 60 to the piezoelectric cell 31. This causes a deformation of the tube 32. According to a second step, the unit 70 measures the voltage supplied by the cell 31 during the time necessary for the tube 32 to return to its initial shape. According to a third step, the unit 70 deduces from the measured voltage a resonance frequency of the resonator 30.

[0026] According to a fourth step, the unit 70 controls the sending of an electrical excitation pulse 84 to the resonator 83. According to a fifth step, the unit 70 measures the voltage supplied by the capsule 80 in response to the excitation. According to a sixth step, the unit 70 deduces from the measured voltage a resonance frequency of the resonator 83.

[0027] According to a sixth step, the unit 70 determines a difference between the resonant frequency of the resonator 30 and the reference frequency of the resonator 83.

[0028] According to a final step, the unit 70 issues an alert when the calculated deviation is greater than a predetermined threshold. The value of the predetermined threshold ideally corresponds to the deviation observable when the lubricant 21 comprises a fuel 41 rate substantially equal to or greater than five percent of fuel 41 in the lubricant 21.

[0029] Of course, the invention is not limited to the embodiment described but encompasses any variant falling within the scope of the invention as defined by the claims.

[0030] In particular, - although here the measuring device is located in a cavity tapped into a pipe, the invention also applies to other configurations in which the measuring device is not placed in a dedicated cavity but in a volume of known dimensions, such as a tank for example or a pipe; - although here the lubrication circuit comprises an instrumented resonator comprising a cylindrical tube and a piezoelectric microphone, the invention also applies to other types of instrumented resonator such as, for example, a tuning fork provided with a resistive strain gauge or a spiral spring provided with an accelerometer; - although here the purity indicator relates to the presence of fuel in the lubricant, the invention also applies to other types of purity indicators such as, for example, indicators relating to the aging of the lubricant, its concentration of additives, its viscosity or its concentration of metal particles; although here the piezoelectric cell performs the functions of exciter and microphone, the invention also applies to a lubrication circuit in which the functions of exciter and microphone are distinct, such as for example an exciter in the form of a tinkling hammer or a piezoelectric or mechanical vibrator distinct from the microphone; although here the piezoelectric cell performs the functions of exciter and microphone, the invention also applies to a lubrication circuit without an exciter and whose resonator would be excited by the surrounding noises, these having been previously analyzed or not.

Claims

Claims

1. Turbomachine (1) comprising a lubrication circuit (20) traversed by a lubricant (21), the lubrication circuit (20) comprising a first instrumented resonator (30), connected to a control and measurement unit (70) arranged to provide an indicator of purity of the lubricant (21).

2. Turbomachine (1) according to claim 1, in which the lubrication circuit (20) comprises an exciter (31) connected to the control and measurement unit (70).

3. Turbomachine (1) according to claim 2, in which the lubrication circuit comprises a temperature sensor (35) of the lubricant (21) connected to the control and measurement unit (70).

4. Turbomachine (1) according to any one of the preceding claims, in which the lubrication circuit (20) comprises a capsule (80) of reference lubricant (81) having a reference purity state, the capsule (80) being arranged so that the reference lubricant (81) is at the same temperature as the lubricant (21), the capsule (80) comprising a second instrumented resonator (83) connected to the control and measurement unit (70).

5. Turbomachine (1) according to any one of the preceding claims, in which the first resonator (30) comprises a piezoelectric type microphone (31).

6. Turbomachine according to any one of the preceding claims, in which the first resonator (30) comprises a cylindrical tube (32) one of the ends (33) of which is closed.

7. Turbomachine (1) according to any one of the preceding claims, wherein the control and measurement unit (70) is arranged to detect the presence of a fuel (41) in the lubricant (21).

8. Turbomachine (1) according to any one of the preceding claims, in which the control and measurement unit (70) is arranged to emit an alarm when a value of the purity indicator shows a deviation relative to a reference value which is greater than a predetermined threshold.

9. Aircraft comprising a turbomachine (1) according to any one of the preceding claims.

10. A method of measuring the purity of a lubricant (21) in a turbomachine according to any one of claims 1 to 8 comprising the following steps: - measuring a resonance frequency of the first resonator (30); - determine a deviation between the measured frequency and a reference value; - issue an alert when the deviation is greater than a predetermined threshold.

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