FR3142505A1 - CHECKING THE OIL QUALITY OF A LUBRICATION OIL CIRCUIT IN AN AIRCRAFT TURBOMACHINE - Google Patents

Abstract

Aircraft turbomachine (T), comprising a lubricating oil circuit and a device (20) for controlling the quality of the oil in said circuit, the lubrication circuit comprising an oil reservoir (10) comprising a port (14) oil outlet, the control device (20) a monitoring system (36) connected to at least one light source (30) and at least one light sensor (34) and configured to calculate an absorbance oil (24) and to compare this absorbance to a threshold value, and to issue an alert when this absorbance is greater than a threshold value. Figure for abstract: Figure 3

Description

CHECKING THE OIL QUALITY OF A LUBRICATION OIL CIRCUIT IN AN AIRCRAFT TURBOMACHINE Technical field of the invention

The present invention relates to controlling the quality of the oil in a lubricating oil circuit in a turbomachine. It relates more precisely to an aircraft turbomachine comprising a lubricating oil circuit and a device for controlling the quality of the oil of this circuit, as well as a method for controlling the quality of the oil of a lubricating oil circuit in this turbomachine.

Technical background

An aircraft turbomachine comprises a lubricating oil circuit which has, in addition to its primary function of lubricating the rotating parts of the turbomachine, an additional function of cooling certain components of the turbomachine.

Lubrication and cooling of the turbomachine parts ensures their proper functioning and optimal lifespan.

It is therefore necessary to control the quality of the oil in the turbomachine lubrication circuit. In current technology, this control is carried out via oil pressure and temperature sensors which are placed in the oil circuit, and an oil level sensor placed in the oil tank. circuit oil. The oil circuit typically includes heat exchangers to allow cooling of the oil by heat exchange with a fluid such as air or fuel. An oil temperature regulation system can be provided capable of controlling, for example, the oil supply valves of the heat exchangers, or the flow rate and/or the temperature of the fluid in heat exchange with the oil, in order to maintain the oil temperature at optimal values during the different phases of engine operation.

Classically, antioxidant additives are present in the formulation of aeronautical oils to protect the lubricating base from rapid thermo-oxidative degradation. The antioxidant level in the oil is an indicator of the quality of the oil and its ability to properly lubricate the engine.

An aircraft turbomachine also has a natural oil consumption which leads to regularly adding new oil to the oil circuit. This new oil has a high antioxidant concentration, and its addition will therefore help to increase the antioxidant concentration of the total oil in the circuit (composed of new oil and oil already used).

Thus, the higher the engine oil consumption, the more regular additions of new oil will be made to the circuit, contributing to a high average antioxidant level in the engine (curve C1 at the ). Conversely, low engine oil consumption will lead to low oil renewal and therefore a low antioxidant level (curve C2 at the ). In the absence of oil consumption, the antioxidants end up disappearing (curve C3 at the ).

It is described in patents US-A-3,509,214 and US-A-5,489,711 that these aromatic antioxidant additives react together in oxidizing media to form oligomers which themselves have antioxidant properties.

These oligomers are therefore beneficial but in too large quantities, they can increase the viscosity of the oil due to the fact that they are high molecular weight compounds (see patent FR-A1-2 924 122). Too high an oligomer concentration is also an indicator of the level of alteration of the oil compared to new oil.

Since the oligomers are formed from aromatic molecules, they are themselves aromatic but with a greater electronic delocalization than in the initial antioxidant additives, which has the effect of stabilizing them and giving them the particular property of absorb visible light. The appearance of these compounds and the associated color therefore tells us about the oxidation conditions seen by the oil and therefore its quality.

Furthermore, the lubricating base of all aeronautical oil is composed of esters. As they age, these themselves generate compounds that absorb UV-Visible radiation.

There shows the appearance of UV-absorbing compounds in an ester oil having undergone thermal aging (from left to right: oil aged 1 week in an oven at 150°C, oil aged 2 weeks in an oven at 150°C, oil aged 3 weeks in an oven at 150°C, oil aged 4 weeks in an oven at 150°C).

Another known technique for controlling the quality of the oil in a turbomachine lubrication circuit consists of taking occasional samples of oil from the circuit, which are then analyzed in the laboratory. This method has the advantage of being precise but not instantaneous and requires long and costly maintenance operations which cannot therefore be carried out regularly in an operational context.

The present invention proposes an improvement to the control devices of the current technique, which makes it possible to monitor the quality of the oil from the monitoring of its composition but without the disadvantages of the prior technique.

The invention proposes an aircraft turbomachine, comprising a lubricating oil circuit and a device for controlling the quality of the oil of said circuit, the lubrication circuit comprising an oil tank comprising an outlet port. oil, characterized in that said control device comprises:

- a first tube connected to the outlet port for the circulation of oil from said circuit through this first tube,

- a second tube containing a reference oil,

- at least one light source configured to emit at least one light radiation through transparent portions of the first and second tubes, this light radiation having a wavelength between predetermined values,

- at least one light sensor configured to receive the light radiation emitted by said at least one source, after passing through the tubes and the oils contained in these tubes, and

- a monitoring system connected to said at least one light source and to said at least one light sensor and configured to calculate an absorbance of the oil of the first tube from signals generated by said at least one sensor, to compare this absorbance at a threshold value, and to issue an alert when this absorbance is greater than the threshold value.

The invention thus proposes a strategy for “online” or “in situ” control of the composition, and for example of oxidation products, of the oil in a turbomachine lubricating oil circuit. This control makes it possible in particular to relax sizing constraints for the same level of oil lubrication, thanks to more in-depth monitoring than is done today (sample collection and sending to the laboratory for analysis). The sizing constraint that can be relaxed is in particular the maximum temperature of the oil in the circuit, this temperature can be increased (while maintaining the same lubrication quality), which allows:

- mass savings thanks to less bulky heat exchangers,

- financial gains from the point of view of engine design thanks to a less complex oil circuit but also from the point of view of fleet operation with non-systematic oil fillings depending on the quality of oil measured.

The control of the oil is carried out by calculating its absorbance to light radiation. In accordance with the Beer-Lambert law, which will be detailed in more detail below, the light absorption of a solution is proportional to the concentration of absorbing molecule of this solution, with respect to a solution of reference, and is calculated from the energy intensities detected by the sensor(s).

The turbomachine according to the invention may comprise one or more of the following characteristics, taken in isolation from each other or in combination with each other:

- the first and second tubes are located next to each other and are separated from each other by an opaque partition at said wavelength;

- the opaque partition is part of a support member which carries said second tube and which is fixed to said tank;

- the first tube is directly connected to the first port or is mounted in parallel with a pipe connected to the first port;

- the first and second tubes have identical shapes and dimensions and are parallel and positioned in a plane which is perpendicular to the light radiation emitted by said at least one light source;

- the first and second tubes have circular or polygonal sections;

- the first and second tubes have a diameter or transverse dimension less than 5cm, and preferably less than or equal to 2cm;

- the first and second tubes each comprise a section transparent at said wavelength, or diametrically opposite windows transparent at said wavelength;

- the control device comprises a single light source or two identical light sources connected to the same electrical power source;

- the control device comprises two light sensors associated respectively with the first and second tubes;

- the first tube is permanently mounted on the tank and the second tube is removably mounted on the tank and comprises for example a threaded end for screwing into an element of the tank;

- the first and second tubes are permanently mounted on the tank, the second tube being connected to the tank by at least one valve so as to be able to isolate the second tube from said circuit after filling this second tube with oil;

- the monitoring system is configured to calculate the absorbance of the oil of the first tube as being the decimal logarithm of the ratio between the energy intensity captured having passed through the reference oil of the second tube and the energy intensity captured having passed through the oil from the first tube;

-- the tank includes an oil inlet port which is connected to a mechanical deaerator;

-- the transparent portions are made of glass or quartz;

-- the monitoring system is of the FADEC type;

-- the or each light sensor is a monochromatic or polychromatic sensor, associated or not with a filter and/or at least one optical element such as a lens; And

-- the control device is mounted directly on the tank and for example at its outlet port.

The invention also relates to a method for controlling the quality of the oil of a lubricating oil circuit in a turbomachine as described above, this method comprising a control step comprising the emission of radiation light at a wavelength between predetermined values, the reception of this light radiation after passing through the tubes and the oils contained in these tubes, and the calculation of the absorbance of the oil of the first tube to control a concentration of aromatic oligomers in the oil of said circuit.

The method according to the invention may comprise one or more of the following characteristics or steps, taken in isolation from each other or in combination with each other:

- the detection step is carried out occasionally at the start and/or at the end of an operating cycle of the turbomachine, and for example when starting and/or stopping the turbomachine;

- the control step comprises the emission and reception of at least one other light radiation at a different wavelength to control a concentration of at least one other compound in the oil of said circuit.

Brief description of the figures

Other characteristics and advantages of the invention will appear during reading of the detailed description which follows, for the understanding of which we will refer to the appended drawings in which:

There is a graph showing the evolution of the concentration (%) of antioxidant in the oil as a function of the duration in hours (h) of use of this oil,

There schematically represents a container containing oil at several stages of aging,

There is a very schematic view of a control device for an aircraft turbomachine, seen from the front,

There is another very schematic view of the control device of the , side view,

There is a view similar to that of the and showing a variant embodiment of the invention, and

Figures 6a to 6d are very schematic views of tubes for the control device according to the invention.

Detailed description of the invention

Figures 1 and 2 have been described in the above.

The present invention relates to an aircraft turbomachine comprising a lubricating oil circuit and a device for controlling the quality of the oil in this circuit.

Conventionally, a turbomachine T comprises a gas generator comprising from upstream to downstream, with reference to the flow of gases in the turbomachine, at least one compressor, an annular combustion chamber, and at least one turbine. The compressor comprises a rotor which is guided in rotation relative to a stator of the compressor and which is connected by a shaft to a rotor of the turbine to form a rotating body. The turbomachine may comprise two or more rotating bodies, for example a low pressure body and a high pressure body.

The turbomachine oil circuit is used to lubricate mechanical parts of the turbomachine such as guide bearings and gear parts, and also to cool them.

Control of the quality of the oil is necessary to guarantee the proper functioning of these parts and of the turbomachine, as well as to optimize their lifespan, and the present invention provides "on-line" control of this quality by controlling of the composition of the oil. This check is therefore carried out in situ directly on the oil circuit.

The lubrication circuit of the turbomachine T includes an oil reservoir 10 which is schematically represented in Figures 3 and 4 by a simple rectangle. The shape of this tank 10 is not limiting. It can be a main or secondary reservoir of the lubrication circuit, so its oil storage capacity by volume is not limiting either.

The tank 10 includes an oil inlet port 12 and an oil outlet port 14. In the example shown, port 12 is located in the upper part of tank 10 and port 14 is located in the lower part or even at the bottom of tank 10, even if these aspects are not limiting.

The inlet port 12 can be connected to a mechanical deaerator 16 which is configured to separate the air contained in the oil which supplies the tank 10. The deaerator makes it possible to minimize the influence of air bubbles on the control. This deaerator 16 can be housed inside the tank 10.

The output port 14 is connected to a pipe 18.

The turbomachine T includes a device 20 for controlling the quality of the oil in the circuit, which can be mounted directly on the tank 10 as in the example shown. It is for example mounted at the outlet port 14 of the tank 10, therefore here in the lower part.

According to one embodiment, the device 20 comprises:

- a first tube 22 connected to the outlet port 14 for the circulation of oil 24 of the circuit through this first tube,

- a second tube 26 containing a reference oil 28,

- at least one light source 30 configured to emit at least one light radiation 32 through the tubes 22, 26,

- at least one light sensor 34 configured to receive the light radiation 32' emitted by the source 30, after passing through the tubes 22, 26 and the oils 24, 28 contained in these tubes, and

- a monitoring system 36 connected to the light source 30 and the light sensor 34.

The first tube 22 can be integrated into the outlet port 14 or into the pipe 18 connected to this outlet port 14, as illustrated in Figures 3 and 4. Alternatively, the first tube 22 could be mounted in parallel to the outlet port 14 or pipe 18, as illustrated in .

To allow the passage of light radiation 32 through it and through the oil 24 which it contains, the first tube 22 can be made of a transparent material, that is to say transparent to the wavelength or at the wavelengths of the radiation. This configuration is illustrated in Figure 6a.

Alternatively, as illustrated in Figure 6b, the first tube 22 may comprise a section 22a of transparent material, the radiation being intended to be emitted through this section 22a.

In yet another variant illustrated in Figure 6c, the first tube 22 may comprise windows 22b made of transparent material, the radiation being intended to be emitted through these windows 22b.

The first tube 22 can have a generally cylindrical shape as illustrated in Figures 6a-6b. The first tube 22 then has a circular cross section.

Alternatively, it could have a general parallelepiped shape as illustrated in Figure 6d. The first tube 22 then has a polygonal cross section and for example square or rectangular. As illustrated in Figures 6a to 6c, the tube 22 of Figure 6d could be entirely transparent or include a transparent section 22a or transparent portholes 22b.

The second tube 26 is advantageously located next to the first tube 22 as in the example shown. It contains a reference oil 28, that is to say a new oil which has not been used in the turbomachine and is dedicated to the control device 20.

The second tube 26 is preferably airtight and airless to minimize oxidation of the oil 28 it contains.

The second tube 26 can be permanently mounted on the tank 10 or removable. In the example shown in Figures 3 and 4, the tube 26 comprises a threaded end 26a for screwing into the tank 10 or an element of the tank or attached to the tank.

In the case where the second tube 26 is permanently mounted, it is preferably connected to the circuit by one or more valves 42, 44. This configuration is shown in dotted lines at the . The tube 26 is connected by a first valve 42 to the tank 10 or to the port 14, and by a second valve 44 to the line 18. When the oil in the circuit is changed with new one, the valves 42, 44 are open so as to circulate this new oil in the tube 26. The valves 42, 44 are then closed so that this new and reference oil remains stored in the tube 26. It will be replaced with a new reference oil during the next oil change and the next replacement of the circuit oil.

In the alternative embodiment of the , the tube 26 is carried by a support 46 which is fixed to the tank 10.

To allow the passage of light radiation 32 through the second tube 26 and through the oil 28 which it contains, the second tube 26 can be of one of the types illustrated in Figures 6a to 6d and described in the above in relation to the first tube 22.

Typically, the transparent materials of the tubes 22, 26 can be glass which has transparency at wavelengths between 340nm and 2500nm, quartz which has transparency at wavelengths between 190nm and 800nm, or even a plastic material such as PC or PMMA.

The tubes 22, 26 preferably have identical shapes and dimensions. They are preferably parallel and positioned vertically in the same plane P (cf. ). This plane P is preferably perpendicular to the light radiation 32 emitted by the light source 30.

The tubes 22, 26 have for example a diameter or a transverse dimension less than 5cm, and preferably less than or equal to 2cm. This diameter or this dimension is for example equal to 1cm.

The tubes 22, 26 are preferably separated from each other by an opaque partition 48 at the wavelengths of the radiation, so as to guarantee that the light sensor(s) 34 which receive(s) the light radiation 32' which has passed through the oil 24 is not disturbed by the light radiation 32' which has passed through the oil 28.

For this, the partition 48 advantageously extends from the source(s) 30 to the sensor(s) 34.

As seen in the drawings, this partition 40 extends in a plane perpendicular to the plane P and parallel to the radiation 32.

The light source 30 is configured to emit at least one light radiation 32 through the transparent portions of the tubes 22, 26. This light radiation 32 has a wavelength between predetermined values which are a function of the compound(s) whose concentration wants to be controlled in the oil.

A single light source 30 can be used to emit light radiation intended for the two tubes 22, 26. In this case, the partition 48 would extend to the front and as close as possible to the source 30, as is visible to the For example.

Alternatively, one or more light sources 30 may be associated with each tube 22, 26, these sources therefore being two or more in number.

The light source 30 may comprise at least one element of reduced size, for example one or more diodes, placed at the focus of a converging lens so as to obtain a parallel beam of light.

The light source(s) 30 are advantageously supplied with electricity by the same current source so as to ensure that their power conditions are identical, which prevents these conditions from having an impact on the detected signals. by the sensor(s) 34.

A single sensor 34 can be used to receive the light radiation 32' which has passed through the two tubes 22, 26. It is understood, however, that, in this case, the emissions and receptions of the radiation cannot be simultaneous. It is first necessary to carry out the emission and reception of a first radiation through the first tube 22, then in a second stage to carry out the emission and reception of a second radiation through the second tube 26.

In a preferred embodiment of the invention, two independent sensors are used so as to simultaneously carry out the emissions and receptions of the radiation 32' which has passed through the two tubes 22, 26.

As illustrated in Figures 3 and 4, the partition 48 preferably extends between the two sensors 34 to avoid the aforementioned drawbacks.

In the case of the , we see that this partition 48 is integrated or forms part of the support 46.

We see in the drawings that the tube 22 is interposed between the light source 30 or one of the light sources, and the sensor 34 or one of the sensors, and that the tube 26 is interposed between the light source 30 or one of the light sources, and the sensor 34 or one of the sensors. The distances between the tubes 22, 26 and the source(s) 30 on the one hand are identical, and the distances between the tubes 22, 26 and the sensor(s) 34 on the other hand are also identical.

The sensors 34 are for example monochromatic or polychromatic sensors.

The monitoring system 36, for example of the FADEC type, is configured to calculate an absorbance of the oil 24 of the first tube 22 from signals generated by the sensor(s) 34, to compare this absorbance to a threshold value, and to issue an alert when this absorbance is greater than the threshold value.

This critical threshold can be determined by preliminary tests because this threshold depends in particular on the architecture and specifications of the engine, particularly on the oil circuit which determines the maximum possible aging of the oil.

According to the Beer-Lambert law, the light absorption A of a solution is proportional to the concentration of absorbing molecule according to the equation:

[MATH1]
A = εlc
in which

ε represents the molar extinction coefficient of the absorbing entity, l represents the length of the path traveled by the light in the medium considered, and c represents the concentration of the absorbing molecule.

Furthermore, the absorbance A can be calculated according to the equation below, as being the decimal logarithm of the ratio between the energy intensity I ₁ at a wavelength crossing a reference medium and the energy intensity I ₂ at the same wavelength , crossing the medium to be characterized.

A =

To measure the quantity of degradation products (antioxidant esters or oligomers) formed during the aging of aeronautical engine oils, it is sufficient to calculate the absorbance of these products. To do this, we measure the energy intensity transmitted through the oil 28 and through the oil 26 supplying the engine oil circuit, at the maximum absorption wavelengths of the products that we wish to control.

Thus, the control device 20 according to the invention makes it possible to calculate the absorbance of the oil 24 relative to that of the oil 28 by applying the second equation with the energy intensity transmitted through the oil 24 and the energy intensity transmitted through the oil 28. Initially, when the oil circuit is filled for the first time, the absorbance will be equal to 0. As it ages, the used oil will produce absorbing UV-visible compounds which will result in a reduction in energy intensity transmitted through the oil 24 of the first tube 22 and therefore an increase in the absorbance A.

The present invention also relates to a method for controlling the quality of the oil in a lubricating oil circuit in a turbomachine T as described above.

This method comprises a control step comprising the emission of light radiation 32 at a wavelength between predetermined values, the reception of this light radiation 32' after passing through the tubes 22, 26 and the oils 24, 28 contained in these tubes, and calculating the absorbance of the oil 24 of the first tube 22 to control a concentration of aromatic oligomers in the oil of said circuit

The detection step is preferably carried out occasionally at the start and/or end of an operating cycle of the turbomachine, and for example when starting and/or stopping the turbomachine.

If a change of engine oil type must take place, an operator can, after carrying out the filling operation, also replace the second tube 26, by unscrewing it for example, and replacing it with a new tube containing the new reference oil.

This control step comprises the emission and reception of at least one other light radiation at a different wavelength to control a concentration of at least one other compound in the oil of said circuit. This can be achieved by the same light source, polychromatic, or by an additional light source, monochromatic or polychromatic.

Claims (16)

Aircraft turbomachine (T), comprising a lubricating oil circuit and a device (20) for controlling the quality of the oil in said circuit, the lubrication circuit comprising an oil reservoir (10) comprising a port (14) oil outlet, characterized in that said control device (20) comprises:
- a first tube (22) connected to the outlet port (14) for the circulation of oil from said circuit through this first tube (22),
- a second tube (26) containing a reference oil (28),
- at least one light source (30) configured to emit at least one light radiation (32) through transparent portions of the first and second tubes (22, 26), this light radiation (32) having a wavelength comprised between predetermined values,
- at least one light sensor (34) configured to receive the light radiation (32') emitted by said at least one source (30), after passing through the tubes (22, 26) and the oils (24, 28) contained in these tubes, and
- a monitoring system (36) connected to said at least one light source (30) and to said at least one light sensor (34) and configured to calculate an absorbance of the oil (24) of the first tube (22) from signals generated by said at least one sensor (34), to compare this absorbance to a threshold value, and to issue an alert when this absorbance is greater than the threshold value. Turbomachine (T) according to claim 1, in which the first and second tubes (22, 26) are located next to each other and are separated from each other by an opaque partition (48) at said wavelength. Turbomachine (T) according to claim 2, in which the opaque partition (48) is part of a support member (46) which carries said second tube (26) and which is fixed to said tank (10). Turbomachine (T) according to one of the preceding claims, in which the first tube (22) is directly connected to the first port (14) or is mounted in parallel with a pipe (18) connected to the first port (14). Turbomachine (T) according to one of the preceding claims, in which the first and second tubes (22, 26) have identical shapes and dimensions and are parallel and positioned in a plane (P) which is perpendicular to the light radiation (32) emitted by said at least one light source (30). Turbomachine (T) according to one of the preceding claims, in which the first and second tubes (22, 26) have circular or polygonal sections. Turbomachine (T) according to one of the preceding claims, in which the first and second tubes (22, 26) have a diameter or a transverse dimension less than 5cm, and preferably less than or equal to 2cm. Turbomachine (T) according to one of the preceding claims, in which the first and second tubes (22, 26) each comprise a section (22a) transparent to said wavelength, or diametrically opposed windows (22b) transparent to said wave length. Turbomachine (T) according to one of the preceding claims, in which the control device (20) comprises a single light source (30) or two identical light sources connected to the same electrical power source. Turbomachine (T) according to one of the preceding claims, in which the control device (20) comprises two light sensors (34) associated respectively with the first and second tubes (22, 26). Turbomachine (T) according to one of the preceding claims, in which the first tube (22) is permanently mounted on the tank (10) and the second tube (26) is removably mounted on the tank (10) and comprises for example a threaded end (26a) for screwing into an element of the tank (10). Turbomachine (T) according to one of claims 1 to 10, in which the first and second tubes (22, 26) are permanently mounted on the tank (10), the second tube (26) being connected to the tank (10) by at least one valve (42, 44) so as to be able to isolate the second tube (26) from said circuit after filling this second tube with oil. Turbomachine (T) according to one of the preceding claims, in which the monitoring system (36) is configured to calculate the absorbance of the oil of the first tube as being the decimal logarithm of the ratio between the energy intensity (I ₁ ) captured having passed through the reference oil (28) of the second tube (26) and the energy intensity (I ₂ ) captured having passed through the oil (24) of the first tube (22). Method for controlling the quality of the oil of a lubricating oil circuit in a turbomachine (T) according to one of the preceding claims, this method comprising a control step comprising the emission of light radiation ( 32) at a wavelength between predetermined values, the reception of this light radiation (32') after passing through the tubes (22, 26) and the oils (24, 28) contained in these tubes, and the calculation of the absorbance of the oil (24) of the first tube (22) to control a concentration of aromatic oligomers in the oil of said circuit. Method according to claim 14, in which the detection step is carried out punctually at the start and/or at the end of an operating cycle of the turbomachine, and for example when starting and/or stopping the turbomachine. A method according to claim 14 or 15, wherein the monitoring step comprises emitting and receiving at least one other light radiation at a different wavelength to control a concentration of at least one other compound in the oil from said circuit.