METHOD AND SYSTEM FOR CONTROLLING THE PERMEABILITY OF A LUBRICATION CIRCUIT OF AN AIRCRAFT TURBOME ENGINE

Description

Domaine technique

[0001] The present invention relates to the field of lubrication systems mounted in an aircraft turbomachine.

[0002] In a well-known way, with reference to the [ Fig.1 [ ] An aircraft turbomachine 101 comprises a gas generator 110 having a compression stage 111 and a turbine stage 112 connected to a drive shaft 102 to rotate a propulsion unit (not shown). The turbomachine 101 extends longitudinally along an X-axis.

[0003] As depicted on the [ Fig.1 The drive shaft 102 extends along the longitudinal axis X of the turbomachine 101 and is guided in rotation at the rear of the gas generator 110 by a rear bearing 103 integral with a housing of the turbomachine 101. As is known, the rear bearing 103 comprises a plurality of bearings 104 mounted between two rings. The drive shaft 102 is inserted into the rear bearing 103.

[0004] When the turbomachine 101 is in operation, the drive shaft 102 rotates on itself, which heats the rear bearing 103. To limit this heating, the turbomachine 101 includes, in a known manner, a lubrication circuit 105 which allows, via injection devices 106 (such as jets for example) to inject oil onto the rear bearing 103 to lubricate it and dissipate heat.

[0005] However, when the turbomachine 101 is shut down, the stored heat dissipates from the hottest parts, causing the cooler parts to overheat. During operation, the rear bearing 103 is oil-cooled and therefore a relatively cold component. In other words, the temperature of the rear bearing 103 rises sharply when the turbomachine 101 is shut down, and the residual oil in the rear bearing 103 heats up. Such significant heating can lead to premature aging and degradation of the oil.

[0006] It is well known that oil overheating leads to the formation of solid deposits on the inner walls of the lubrication system passages. This formation of solid particles is commonly referred to as coking. The accumulation of these deposits can clog the lubrication system passages, particularly the injection components, potentially impeding oil circulation. Impaired oil circulation in the lubrication system can lead to degraded turbomachine cooling. Degraded lubrication and cooling can cause premature wear of the rear bearing, which can ultimately damage the turbomachine.

[0007] It is also necessary to regularly check that the lubrication system is not blocked. This involves monitoring the oil flow rate within the lubrication system, particularly at the oil injection points.

[0008] In this regard, a verification method is known in the prior art in which oil is manually poured into the lubrication circuit during a maintenance operation. The oil flows by gravity through the lubrication circuit between an oil inlet and outlet, via the injection devices, for a specified test duration. This test duration is compared to a reference duration, for example, determined after the turbomachine was manufactured, to determine if the flow rate is lower than initially, that is, if its permeability has decreased.

[0009] However, the flow duration depends directly on the exact volume of oil passing through the lubrication circuit, as well as its temperature. Since this operation is not performed in a controlled environment (such as a laboratory), the results are imprecise and prone to errors. Therefore, it is generally necessary to repeat the verification process to confirm the measurements, which is time-consuming. Furthermore, because the turbomachine is mounted on the aircraft, the lubrication circuit inlet is difficult to access and requires an operator to be positioned on the aircraft while the turbomachine cowling is open, which is impractical. In addition, it necessitates maintaining a database with the reference flow durations for each turbomachine, which is complex.

[0010] Also known in the prior art is US patent 3582928A, which describes a system for monitoring the health of an aircraft turbomachine bearing. This system includes a drive shaft, a ball bearing, oil inlet and outlet passages, and a pair of thermocouples for measuring the oil temperature in these passages. The temperature difference between the upstream and downstream passages is compared to a threshold value that depends on the shaft speed, triggering an alert if this difference exceeds the threshold. Furthermore, patent JPS6198925A discloses a monitoring device for the bearings of a gas turbine power generator, a gearbox, and a generator, incorporating lubricating oil inlet and outlet temperature sensors. The measured temperature difference is compared to a threshold value, which is a function of the gas turbine's power output, and then displayed to the user.

[0011] The invention aims to eliminate at least some of these drawbacks by providing a simple, precise, and efficient system and method for checking the permeability of a lubrication circuit in an aircraft turbomachine. The system and method are specifically designed to detect blockages in the lubrication circuit quickly and easily, for example, to enable predictive maintenance. PRESENTATION DE L'INVENTION

[0012] The invention relates to a method for checking the permeability of a lubrication circuit of an aircraft turbomachine, the turbomachine comprising at least one guide bearing in which a propulsion shaft is rotatably mounted, the lubrication circuit being configured to circulate an upstream-downstream flow of oil between an oil inlet of the lubrication circuit and an oil outlet of the lubrication circuit to lubricate the guide bearing, the method comprising the steps of: Measure a first oil temperature upstream of the guide bearing, Measure a second oil temperature downstream of the guide bearing, Calculate a temperature difference between the second temperature and the first temperature, Compare the temperature difference with a predetermined expected temperature difference, and When the temperature difference is greater than the expected temperature difference, emit a lubrication circuit permeability fault signal.

[0013] The method according to the invention allows for the simple and effective detection of a permeability defect in the lubrication circuit. Advantageously, the method, which is easy to implement, enables such control by measuring only the temperature upstream and downstream of the guide bearing. Furthermore, thanks to the invention, it is not necessary to know the initial condition of the new turbomachine, as was the case in the prior art. A temperature measurement is very reliable since, according to one aspect of the invention, the temperature variation of the oil is greater, for example, than a pressure measurement when the circulation channels are obstructed.

[0014] Furthermore, the method according to the invention is precise and advantageously requires only one measurement, unlike the prior art method in which it was necessary to repeat the operation to obtain a reliable result. The inspection method is thus faster and can also be carried out at any time. In other words, thanks to the invention, the inspection method does not require dedicated maintenance, which represents a significant time saving and helps to reduce costs.

[0015] The invention also relates to a method for checking the permeability of a lubrication circuit of an aircraft turbomachine, the turbomachine extending along a longitudinal axis oriented from back to front and comprising successively along the longitudinal axis at least one rear guide bearing, one front guide bearing, in which a drive shaft is rotatably mounted, and a lubrication housing comprising at least one mechanical pump for circulating an oil flow and a device for transmitting the oil pressure and temperature, the lubrication circuit being configured to circulate the oil flow from upstream to downstream between an oil inlet of the lubrication circuit and an oil outlet of the lubrication circuit to lubricate each guide bearing, the method comprising the steps of: Measure a first oil temperature upstream of one of the guide bearings, the first temperature being measured by means of a first oil flow temperature measuring device, mounted in the lubrication housing at the front of the front bearing, Measure a second oil temperature downstream of said guide bearing, Calculate a temperature difference between the second temperature and the first temperature, Compare the temperature difference with a predetermined expected temperature difference, and When the temperature difference is greater than the expected temperature difference, emit a lubrication circuit permeability fault signal.

[0016] The first temperature measurement is taken upstream of the oil inlet to the bearing, at a distance from the bearing itself. This initial measurement is performed using a measuring device already present in the engine's lubrication housing, eliminating the need for an additional measuring device. Furthermore, this first temperature measurement is independent of the bearing and can be used regardless of whether the second temperature measuring device is located downstream of the rear or front bearing.

[0017] The lubrication unit is easily accessible for maintenance and is conveniently located away from the bearings. The initial temperature measurement is easily accessible without increasing complexity or size.

[0018] In a preferred embodiment, with the turbomachine operating at a predetermined speed, the expected temperature difference is predetermined for that speed. For a given speed, the method according to the invention advantageously allows for the determination of an expected temperature difference between the inlet and outlet of the lubrication circuit. Indeed, at constant speed, such a temperature difference is straightforward to determine.

[0019] In one embodiment, the process includes a step of determining a degree of permeability of the lubrication circuit from a database associating a temperature difference and a degree of permeability, the degree of permeability being determined from the temperature difference obtained.

[0020] Thanks to the invention, the degree of permeability can be determined simply and quickly from the temperature difference between the upstream and downstream sides of the guide bearing. This method thus provides an alert in case of excessive obstruction of the lubrication circuit, ensuring optimal operation of the lubrication system.

[0021] In one embodiment, a first temperature difference is calculated at a first instant, and a second temperature difference is calculated at a subsequent instant. The process includes a step of comparing the first and second temperature differences to determine the evolution of the permeability of the lubrication circuit. Monitoring the evolution of the temperature difference advantageously allows for the detection of a decrease in oil flow rate, thus enabling the anticipation of a significant permeability defect and, consequently, a lubrication problem in the turbomachine. Maintenance operations can then be planned in advance, which is beneficial.

[0022] The invention also relates to a computer program type product, comprising at least one sequence of instructions stored and readable by a processor and which, once read by this processor, causes the execution of the steps of the process as previously presented.

[0023] The invention further relates to a computer-readable medium containing the computer program-type product as previously described.

[0024] The invention also relates to a motor system for implementing the method of controlling the permeability of a lubrication circuit as described above, the motor system comprising: an aircraft turbomachine comprising: at least one guide bearing to be monitored in which a drive shaft is rotatably mounted, a lubrication circuit for lubricating the guide bearing, the lubrication circuit being configured to circulate an upstream-downstream flow of oil between an oil inlet of the lubrication circuit and an oil outlet of the lubrication circuit, a first oil flow temperature measuring device, the first measuring device, mounted upstream of the guide bearing in the lubrication circuit, being configured to measure a first oil temperature, a second oil flow temperature measuring device, the second measuring device, mounted downstream of the guide bearing in the lubrication circuit, being configured to measure a second oil temperature, a computer configured to: Calculate a temperature difference between the second temperature and the first temperature,Compare the calculated temperature difference with a predetermined expected temperature difference stored in the computer, and when the temperature difference is greater than the expected temperature difference, emit a lubrication circuit permeability fault signal.

[0025] The engine system according to the invention allows the process to be implemented using simple temperature measuring devices positioned upstream and downstream of the guide bearing. The engine system thus does not require the addition of significant extra devices that would increase the mass and size of the turbomachine. Furthermore, the measuring devices can advantageously be mounted simply and quickly on existing aircraft.

[0026] Preferably, the computer is configured to determine the expected temperature difference from a given turbomachine operating speed.

[0027] The invention also relates to a motor system for implementing the method of controlling the permeability of a lubrication circuit as described above, the motor system comprising: an aircraft turbomachine extending along a longitudinal axis and comprising: successively along the longitudinal axis, at least one rear guide bearing, one front guide bearing, to be monitored, in which a drive shaft is rotatably mounted, and a lubrication housing comprising at least one mechanical pump for circulating an oil flow, and an oil pressure and temperature transmission device, a lubrication circuit for lubricating each guide bearing, the lubrication circuit being configured to circulate the oil flow from upstream to downstream, between an oil inlet of the lubrication circuit and an oil outlet of the lubrication circuit, a first oil flow temperature measuring device, the first measuring device, mounted upstream of each guide bearing in the lubrication circuit, being configured to measure a first oil temperature,The first measuring element being mounted in the lubrication housing at the front of the front bearing, a second measuring element for the oil flow temperature, the second measuring element, mounted downstream of the guide bearing in the lubrication circuit, being configured to measure a second oil temperature, a computer configured to: Calculate a temperature difference between the second temperature and the first temperature, Compare the calculated temperature difference with a predetermined expected temperature difference stored in the computer, and When the temperature difference is greater than the expected temperature difference, output a lubrication circuit permeability fault signal.

[0028] In one embodiment, the computer is configured to determine a degree of permeability of the lubrication circuit from a database accessible by the computer associating a temperature difference and a degree of permeability, the degree of permeability being determined from the temperature difference obtained.

[0029] Preferably, the expected temperature difference depends on a predetermined turbomachine operating condition. Therefore, for a known turbomachine operating condition and a calculated temperature difference, it is straightforward to determine the permeability of the lubrication circuit. Advantageously, no special handling by an operator is required. In particular, access to a specific lubrication circuit inlet, as was the case in the prior art, is not necessary.

[0030] In a first embodiment, the first measuring element includes a pressure and temperature transmission element located in the lubrication circuit upstream of the guide bearing to be monitored, allowing the addition of additional devices to be limited.

[0031] Alternatively, the first measuring element is a sensor mounted separately in the lubrication circuit upstream of the guide bearing to be monitored, which allows for optimal calibration of the measuring element.

[0032] In a first embodiment, the lubrication circuit includes at least one plug, and the second measuring element is mounted on this plug. This plug is used for draining and allows access to the second temperature reading upstream of the guide bearing. Preferably, the second measuring element is an adhesive patch that allows the oil temperature to be determined indirectly by measuring the plug temperature.

[0033] In one embodiment, the second measuring element is a heat-sensitive adhesive patch stuck onto the cap.

[0034] Such an adhesive patch can be easily and quickly fitted onto an existing plug, thus reducing the need to replace parts in the lubrication system. Furthermore, this measuring device allows for a simple and rapid temperature reading.

[0035] Preferably, the second measuring device is a removable adhesive patch. This allows for quick and easy installation during any maintenance operation (not specifically for the lubrication system), for example, and removal at the end of the maintenance. A removable patch also minimizes the risk of damaging the lubrication system components, as no mechanical tools are required for its installation. Furthermore, such a patch is inexpensive. In other words, the permeability of the lubrication system can be easily monitored using the first measuring device located in the pressure and temperature transmission unit found on all engines, and by simply adding a removable patch.

[0036] In one embodiment, the stopper is a magnetic stopper.

[0037] In one embodiment, the lubrication circuit includes at least one plug and the second measuring element is mounted in said plug.

[0038] In a second embodiment, the second measuring element is a temperature probe mounted directly in the cap, allowing direct temperature measurement of the oil flow, which allows for a reliable result.

[0039] In a third embodiment, the second measuring element includes a temperature sensor integrated into the cap, which reduces the bulk while obtaining a reliable temperature reading.

[0040] In a fourth embodiment, the second measuring element comprises a temperature sensor mounted in a circulation channel of the lubrication system. This embodiment allows for reliable temperature measurement of the oil flow moving within the lubrication circuit.

[0041] The invention also relates to an aircraft comprising at least one engine system as described above. PRESENTATION DES FIGURES

[0042] 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 [ Fig.1 ] is a schematic representation of an engine system comprising an aircraft turbomachine and a lubrication circuit according to the prior art. The [ Fig.2 [ ] is a schematic representation of an engine system comprising an aircraft turbomachine and a lubrication circuit according to one embodiment of the invention. The [ Fig.3 ] is a schematic representation of the lubrication circuit of the [ Fig.2 ]. There [ Fig.4 ] is a graph representing the evolution of the temperature difference between the inlet and outlet of the lubrication circuit as a function of the oil circulation flow rate in the lubrication circuit of the [ Fig.3 ]. There [ Fig.5 ] is a schematic representation of a database associating, for a plurality of engine regimes, a flow rate with an expected temperature difference of the [ Fig.3 ]. There [ Fig.6 ] is a diagram of the steps of a control process according to an implementation method of the invention.

[0043] It should be noted that the figures explain the invention in detail for implementing the invention, said figures being of course able to serve to better define the invention where appropriate. DESCRIPTION DETAILLEE DE L'INVENTION

[0044] With reference to the [ Fig.2 ] and to the [ Fig.3 [ ] An aircraft engine system (SM) is shown according to one embodiment of the invention. The engine system (SM) comprises a turbomachine 1 including a lubrication circuit 5 which injects oil to lubricate the turbomachine 1 and dissipate heat, so as to limit the risk of overheating of the turbomachine 1.

[0045] With reference to the [ Fig.2 In this example, the turbomachine 1 extends longitudinally along an axis X. In the remainder of this document, the terms "front" and "rear" are defined with respect to the longitudinal axis X, which extends from the rear to the front of the turbomachine 1. As is known, the turbomachine 1 comprises a gas generator 10 with a compression stage 11 and a turbine stage 12 connected to a drive shaft 2 to rotate a propulsion unit (not shown). The turbomachine 1 is configured to operate at an engine speed R.

[0046] As depicted on the [ Fig.2 The drive shaft 2 extends along the longitudinal axis X of the turbomachine 1. The drive shaft 2 is guided in rotation about the longitudinal axis X by a plurality of guide bearings 3, 4 mounted in the housing of the turbomachine 1. More specifically, the drive shaft 2 is guided in rotation at the rear of the gas generator 10 by a rear bearing 3 and at the front of the gas generator 10 by a front bearing 4. As is known, each guide bearing 3, 4 comprises a plurality of bearings 31, 41 mounted between two rings. The drive shaft 2 is inserted into each of the guide bearings 3, 4. The guide bearings 3, 4 will not be described in further detail in this document.

[0047] The lubrication circuit 5 is configured to limit the heating of the turbomachine 1 due to the rotation of the drive shaft 2 and therefore to the friction between the various components of the turbomachine 1. To achieve this, the lubrication circuit 5 is configured to inject oil into the turbomachine 1, specifically at the guide bearings 3 and 4. The lubrication circuit 5 is then described for the lubrication of a guide bearing 3 or 4 to be monitored. In this example, the guide bearing 3 or 4 to be monitored corresponds to the rear bearing 3; however, it could alternatively be the front bearing 4. Similarly, the circulation of oil in the guide bearings 3 and 4, and in particular in the rear bearing 3, is described below, but it should be understood that the lubricating oil circulates through several components of the turbomachine 1.

[0048] With reference to the [ Fig.2 ] and to the [ Fig.3 ], the lubrication circuit 5 extends into the turbomachine 1 on either side of the rear bearing 3. The lubrication circuit 5 comprises an oil inlet 51, an oil outlet 52, and a plurality of oil circulation lines 53 mounted between the oil inlet 51 and the oil outlet 52. An oil flow H (shown on the [ Fig.2 [ ] by continuous arrows) circulates in the lubrication circuit 5 from upstream to downstream from the oil inlet 51 to the oil outlet 52. In other words, the lubrication circuit 5 extends upstream and downstream of the rear bearing 3. In this example, as shown on the [ Fig.2 ], by "oil inlet" 51 and "oil outlet" 52, we mean the inlet and outlet of the oil in the gas generator 10. The oil inlet 51 and the oil outlet 52 could alternatively be placed in different positions respectively upstream and downstream of the rear bearing 3.

[0049] More specifically, as depicted on the [ Fig.3 ], the lubrication circuit 5 includes a storage tank 55 for the oil H and a mechanical pump 56 for circulating the oil H through the circulation lines 53. The oil H is then configured to flow through the entire turbomachine 1. In particular, the oil H is configured to enter via the oil inlet 51, pass through the rear bearing 3, and exit via the oil outlet 52. To pass through the rear bearing 3, the lubrication circuit 5 includes an injection device 54 (shown in the [ Fig.2 mounted directly upstream of the rear bearing 3. The oil flow H is then configured to circulate in the lubrication circuit 5 at the outlet of the rear bearing 3 by means of a second mechanical pump 56A. The lubrication circuit 5 also includes a cooling device 57 configured to cool the oil flow H after it has been heated in the circulation channels 53, for example, by contact with the bearings of the rear bearing 3.

[0050] More specifically, with reference to figures 2 et 3 The turbomachine 1 includes a service system EQ which comprises several aircraft components. In particular, the service system EQ includes a lubrication housing 8 in which the mechanical oil circulation pump 56 is mounted. The lubrication housing 8 is mounted along the longitudinal axis X in front of the forward bearing 4 to facilitate its accessibility. In other words, the lubrication housing 8 is mounted externally to the gas generator 10.

[0051] In one embodiment, the lubrication circuit 5 includes a pressure and temperature transmission element TR, configured to measure the pressure and temperature of the oil flow H circulating in the lubrication circuit 5. Preferably, the transmission element TR is positioned on the lubrication circuit 5 between the first mechanical pump 56 and the oil inlet 51 of the rear bearing 3. In other words, the transmission element TR is mounted upstream of the rear bearing 3. In practice, the transmission element TR is mounted in the lubrication housing 8. The transmission element TR transmits the pressure and temperature of the oil flow H to a computer in order to communicate information or an alarm to the pilot when necessary.

[0052] Preferably, the lubrication circuit 5 also includes a filter 58 mounted on the lubrication circuit 5 between the first mechanical pump 56 and the oil inlet 51 of the rear bearing 3. Even more preferably, the filter 58 is mounted on the lubrication circuit 5 between the first mechanical pump 56 and the transmission component TR. In other words, the filter 58 is mounted in the lubrication housing 8. The filter 58 retains particles present in the oil, so as to recirculate clean oil in the lubrication circuit 5 and thus limit any risk of obstruction of the lubrication circuit 5.

[0053] In a preferred form of realization, always with reference to the [ Fig.3 ], the lubrication circuit 5 also includes a plug, for example a magnetic plug BM, mounted on the lubrication circuit 5 downstream of the oil outlet 52 of the rear bearing 3. Such a magnetic plug BM generally includes a filter, for example a strainer, and is mounted on the lubrication circuit 5 so as to retain the largest particles of impurities present in the oil at the outlet of the guide bearings 3, 4.

[0054] According to one aspect of the invention, the SM engine system comprises a first measuring element 6 and a second measuring element 7 of the temperature of the oil flow H. As such, each measuring element 6, 7 preferably comprises a temperature sensor.

[0055] As depicted on the figures 2 et 3 The first measuring element 6 is mounted upstream of the rear bearing 3 and is configured to measure a first temperature T1 of the oil H in the lubrication circuit 5 upstream of the rear bearing 3. The second measuring element 7 is mounted downstream of the rear bearing 3 and is configured to measure a second temperature T2 of the oil H in the lubrication circuit 5 downstream of the rear bearing 3. As described previously, the first measuring element 6 and the second measuring element 7 could alternatively be mounted upstream and downstream of the front bearing 4.

[0056] Preferably, the first measuring element 6 includes the transmission element TR.

[0057] In a first embodiment, the first measuring element 6 corresponds to the transmission element TR mounted on the lubrication circuit 5 upstream of the rear bearing 3, which makes it possible to limit the addition of additional elements in the lubrication circuit 5. In addition, the transmission element TR positioned in front of the gas generator 10, i.e. at a distance from the bearings 3, 4, allows a first temperature measurement regardless of which guide bearing 3, 4 is being monitored.

[0058] In a second embodiment, the first measuring element 6 is a sensor mounted separately on the lubrication circuit 5. For example, the first measuring element 6 is in the form of an adhesive patch affixed to one of the circulation channels 53 of the lubrication circuit 5 in order to measure the temperature of a circulation channel 53 and deduce the temperature of the oil H. Such an embodiment allows the first measuring element 6 to be mounted simply and quickly and also allows the first measuring element 6 to be easily added to existing SM engine systems.

[0059] Alternatively, the first measuring element 6 may be in the form of a temperature sensor, for example a probe, mounted inside one of the circulation conduits 53. The first measuring element 6 could alternatively be in a different form, for example in the form of a temperature measuring probe positioned in contact with one of the circulation conduits 53. The first measuring element 6 could also be positioned at the level of an instrumented supply conduit.

[0060] In one embodiment, the second measuring element 7 is in the form of an adhesive patch affixed to one of the circulation channels 53 of the lubrication circuit 5 downstream of the rear bearing 3. The adhesive patch could alternatively be affixed to the magnetic plug BM. It is understood that the second measuring element 7 could be affixed to a different plug.

[0061] An adhesive patch affixed to the magnetic plug BM can be installed quickly and easily, without the need to dismantle any component of the lubrication circuit 5. In this embodiment, the first measuring element 6, corresponding to the transmission element TR mounted in the lubrication housing 8, and the second measuring element 7, corresponding to an adhesive patch affixed to the magnetic plug BM, allow the upstream and downstream temperatures of the bearing 3, 4 to be monitored to be determined without requiring extensive preparation. Applying a single adhesive patch allows the temperature difference in the lubrication circuit 5 to be measured between the upstream and downstream sides of one of the bearings 3, 4, thus significantly reducing maintenance costs and downtime. Furthermore, this can be implemented on any existing engine type without requiring any dismantling or replacement of parts.

[0062] Preferably, the adhesive patch is heat-sensitive and allows, for example, the temperature to be read by a change of color or directly on a graduated scale, allowing the temperature to be determined simply and quickly.

[0063] Ideally, the adhesive patch should be removable. This allows the second measuring element to be easily removed after maintenance.

[0064] In an alternative embodiment, the second measuring element 7 is a temperature probe mounted directly in the magnetic plug BM or in one of the circulation channels 53, thus enabling a reliable and direct measurement. Alternatively, the second measuring element 7 could take a different form, for example, a temperature measuring probe positioned in contact with one of the circulation channels 53. The second measuring element 7 could also be mounted in an oil recovery channel.

[0065] Still referring to the [ Fig.3 The SM engine system includes a control unit 9, preferably electrically connected to the first measuring element 6 and the second measuring element 7. The control unit 9 is configured to receive a first temperature T1 measured by the first measuring element 6 upstream of the rear bearing 3 and a second temperature T2 measured by the second measuring element 7 downstream of the rear bearing 3, and to calculate a temperature difference ΔT between the second temperature T2 and the first temperature T1 (ΔT = T2 - T1). Alternatively, the first temperature T1 and the second temperature T2 could be recorded (e.g., read from an adhesive patch) by an operator who could enter the values ​​into the control unit 9. The control unit 9 can be integrated into an engine monitoring module, also known as "Health Monitoring".

[0066] The control unit 9 is also configured to compare the temperature difference ΔT with a predetermined expected temperature difference ΔT0. The expected temperature difference ΔT0 preferably corresponds to a specific operating speed R of the turbomachine 1. When the temperature difference ΔT is greater than the expected temperature difference ΔT0, the control unit 9 is configured to output a permeability fault signal from the lubrication circuit 5.

[0067] Indeed, as shown on the [ Fig.4 For a given operating regime R (RA, RB, ...) of the turbomachine 1, the temperature difference ΔT varies according to the flow rate D of the oil flow H in the lubrication circuit 5 (and more specifically in the rear bearing 3). More precisely, for a given operating regime R, the lower the flow rate D of the oil flow H, the higher the temperature difference ΔT between the upstream and downstream sides of the rear bearing 3. According to one aspect of the invention, a temperature difference ΔT greater than the expected temperature difference ΔT0 indicates that the flow rate D of the oil flow H in the lubrication circuit 5 is insufficient. In other words, the lubrication circuit 5 is obstructed and its permeability is limited. By "limited permeability," we mean that an insufficient quantity of oil circulates in the lubrication circuit 5 to optimally lubricate the turbomachine 1.

[0068] In one embodiment, the calculator 9 is further configured to determine a degree of permeability DP of the lubrication circuit 5 from the temperature difference ΔT obtained for the determined operating regime R. Preferably, the degree of permeability DP is determined from a database associating an operating regime R, a temperature difference ΔT, and a degree of permeability DP.

[0069] As such, he is represented on the [ Fig.5 ], an example of a database BdD in which for a given regime RA (RB, ... RX), each temperature difference ΔTA-1, ΔTA-2, ΔTA-3, ... (ΔTB-1, ΔTB-2, ..., ΔTX-1, ΔTX-2, ...) is associated with a degree of permeability DPA-1, DPA-2, DPA-3, ... (DPB-1, DPB-2, ..., DPX-1, DPX-2, ...).

[0070] In one embodiment, the computer 9 is configured to calculate, at a first instant, a first temperature difference ΔT1 between the first temperature T1 and the second temperature T2 and, at a second instant, subsequent to the first instant, a second temperature difference ΔT2 between the first temperature T1 and the second temperature T2. The computer 9 is then configured to compare the first temperature difference ΔT1 and the second temperature difference ΔT2 and to determine the change in the temperature difference ΔT between the first and second instants. This embodiment makes it possible to anticipate the obstruction of the rear bearing 3 of the lubrication circuit 5 by detecting an increase in the temperature difference ΔT corresponding to a decrease in the flow rate D.

[0071] A method for determining the permeability of a lubrication circuit 5 of an aircraft turbomachine 1 will now be described according to an embodiment of the invention, with reference to the [ Fig.6 In this example, an oil flow H circulates in the lubrication circuit 5 and, more specifically, flows from upstream to downstream in the gas generator 10 via the guide bearing 3, 4 to be monitored. The method will be described for monitoring the rear bearing 3; however, the method according to the invention also applies to monitoring the front bearing 4. Similarly, for a turbomachine 1 comprising a different number of guide bearings, the invention applies with the same advantages to any guide bearing of an aircraft turbomachine. In this example, the turbomachine 1 operates at a predetermined speed R.

[0072] According to the invention, the permeability of the lubrication circuit 5 is determined from a temperature difference between the upstream and downstream of the guide bearing 3, 4 to be monitored, in this example the rear bearing 3. For this, in this example, the first measuring element 6 comprises the transmission element TR mounted in the lubrication housing 8 at the front of the front bearing 4 and the second measuring element 7 is an adhesive patch glued on the magnetic plug BM.

[0073] The process includes a first step E1 of measurement, by the first measuring element 6 of a first temperature T1 of the oil flow H upstream of the rear bearing 3 and by the second measuring element 7 of a second temperature T2 of the oil flow H downstream of the rear bearing 3.

[0074] In a second step E2, the computer 9 calculates a temperature difference ΔT between the upstream and downstream sides of the rear bearing 3 (ΔT=T2-T1). The computer 9 then compares, in a step E3, the calculated temperature difference ΔT with a predetermined expected temperature difference ΔT0 for the specified operating speed R of the turbomachine 1.

[0075] In one embodiment, the computer 9 determines, in step E4, a degree of permeability DP of the lubrication circuit 5 from the temperature difference ΔT obtained for the determined operating regime R. To do this, the computer 9 determines the degree of permeability DP from a database BdD which associates, for the determined operating regime of the turbomachine 1, a degree of permeability DP-1, DP-2, ... with a temperature difference ΔT-1, ΔT-2, ....

[0076] When the calculated temperature difference ΔT is greater than the expected temperature difference ΔT0, the computer 9 detects that the permeability of the lubrication circuit 5 is insufficient and emits a signal of lubrication circuit 5 permeability fault, in a step E5.

[0077] Indeed, the temperature difference ΔT is directly related to the flow rate D of the oil flow H in the lubrication circuit 5. Also, when the rear bearing 3 is obstructed, for example by the presence of deposits, the flow rate of the oil flow H decreases, the permeability of the rear bearing 3 (and therefore of the lubrication circuit 5) is limited.

[0078] In one embodiment, the control unit 9 calculates, at a first instant, a first temperature difference ΔT1 between the first temperature T1 and the second temperature T2. At a second instant, the control unit 9 calculates a second difference ΔT2 between the first temperature T1 and the second temperature T2. The control unit 9 then compares the first temperature difference ΔT1 and the second temperature difference ΔT2 and determines the change in the temperature difference ΔT between the first and second instants. If an increase in the temperature difference ΔT is detected between the first and second instants, the control unit 9 sends, in this example, an alert signal corresponding to the detection of a decrease in the flow rate D. In this example, such an alert signal is emitted even when the oil flow H is still sufficient.Such a form of implementation makes it possible, for example, to anticipate a subsequent control, making it possible not to wait until the lubrication circuit 5 is functioning in a degraded manner.

[0079] The determination method according to the invention makes it possible to prevent obstruction of the lubrication circuit, and more specifically of the guide bearing to be monitored, in a simple and rapid manner by calculating a temperature difference between the upstream and downstream sides of said guide bearing. Such a measurement can be carried out at any time during any maintenance operation (not specifically for the lubrication circuit), or even while the aircraft is in flight.

Claims

1. A method for controlling the permeability of a lubrication circuit (5) for an aircraft turbomachine (1), the turbomachine (1) extending along a longitudinal axis (X) oriented from rear to front and comprising successively along the longitudinal axis (X) at least one rear guide bearing (3), a front guide bearing (4), wherein a propulsion shaft (2) is rotatably mounted, and a lubrication box (8) comprising at least one mechanical pump (56) for circulating a flow of oil (H) and a member (TR) for transmitting the pressure and the temperature of the oil, the lubrication circuit (5) being configured to circulate the flow of oil (H) from upstream to downstream between an oil inlet (51) of the lubrication circuit (5) and an oil outlet (52) of the lubrication circuit (5) in order to lubricate each guide bearing (3, 4), the method comprising the steps consisting in: - Measuring a first temperature (T1) of the oil upstream of one of the guide bearings (3, 4), the first temperature (T1) being measured by means of a first member (6) for measuring the temperature of the flow of oil (H), mounted in the lubrication box (8) in front of the front bearing (4), - Measuring a second temperature (T2) of the oil downstream of said guide bearing (3, 4), - Calculating a temperature difference (ΔT) between the second temperature (T2) and the first temperature (T1), - Comparing the temperature difference (ΔT) with a predetermined expected temperature difference (ΔT0), and - When the temperature difference (ΔT) is greater than the expected temperature difference (ΔT0), signaling a permeability fault in the lubrication circuit (5).

2. The control method as claimed in claim 1, wherein, with the turbomachine (1) operating at a given regime (R), the expected temperature difference (ΔT0) is predetermined for the given regime (R).

3. The control method according to one of claims 1 to 2, comprising a step of determining a degree of permeability (DP) of the lubrication circuit (5) from a database (BdD) associating a temperature difference (ΔT) and a degree of permeability (DP), the degree of permeability (DP) being determined from the temperature difference (ΔT) obtained.

4. The control method according to one of claims 1 to 3, wherein, a first temperature difference (ΔT1) being calculated at a first instant, a second temperature difference (ΔT2) being calculated at a second instant, subsequent to the first instant, the method comprises a step of comparing the first temperature difference (ΔT1) and the second temperature difference (ΔT2), so as to determine a change in the permeability of the lubrication circuit (5).

5. A product of the computer program type, comprising at least one sequence of instructions stored and readable by a processor and which, once read by this processor, leads the engine system (SM) according to one of claims 6 to 13 to carry out the steps of the method according to one of claims 1 to 4.

6. An engine system (SM) for implementing the method for controlling the permeability of a lubrication circuit (5) according to one of claims 1 to 4, the engine system (SM) comprising: - an aircraft turbomachine (1) extending along a longitudinal axis (X) and comprising: o successively along the longitudinal axis (X), at least one rear guide bearing (3), a front guide bearing (4), to be monitored, wherein a propulsion shaft (2) is rotatably mounted, and a lubrication box (8) comprising at least one mechanical pump (56) for circulating a flow of oil (H), and a member (TR) for transmitting the pressure and the temperature of the oil, o a lubrication circuit (5) for lubricating each guide bearing (3, 4), the lubrication circuit (5) being configured to circulate the flow of oil (H) from upstream to downstream, between an oil inlet (51) of the lubrication circuit (5) and an oil outlet (52) of the lubrication circuit (5), - a first member (6) for measuring the temperature of the flow of oil (H), the first measuring member (6), mounted upstream of each guide bearing (3, 4) in the lubrication circuit (5), being configured to measure a first temperature (T1) of the oil, the first measuring member (6) being mounted in the lubrication box (8) in front of the front bearing (4), - a second member (7) for measuring the temperature of the flow of oil (H), the second measuring member (7), mounted downstream of the guide bearing (3, 4) in the lubrication circuit (5), being configured to measure a second temperature (T2) of the oil, - a calculator (9) configured for: o Calculating a temperature difference (ΔT) between the second temperature (T2) and the first temperature (T1), o Comparing the calculated temperature difference (ΔT) with a predetermined expected temperature difference (ΔT0) stored in the calculator (9), and o When the temperature difference (ΔT) is greater than the expected temperature difference (ΔT0), signaling a permeability fault in the lubrication circuit (5).

7. The engine system (SM) according to claim 6, wherein the calculator (9) is configured to determine a degree of permeability (DP) of the lubrication circuit (5) from a database (BdD) accessible by the calculator (9) and associating a temperature difference (ΔT) and a degree of permeability (DP), the degree of permeability (DP) being determined from the temperature difference (ΔT) obtained.

8. The engine system (SM) according to one of claims 6 to 7, wherein the first measuring member (6) comprises a pressure and temperature transmission member (TR) located in the lubrication circuit (5) upstream of the guide bearing (3, 4) to be monitored.

9. The engine system (SM) according to one of claims 6 to 8, wherein the lubrication circuit (5) comprises at least one plug (BM) and the second measuring member (7) is mounted on said plug (BM).

10. The engine system (SM) according to claim 9, wherein the second measuring member (7) is a heat-sensitive adhesive patch glued to the plug (BM).

11. The engine system (SM) according to claim 10, wherein the second measuring member (7) is a removable adhesive patch.

12. The engine system (SM) according to one of claims 6 to 8, wherein the lubrication circuit (5) comprises at least one plug (BM) and the second measuring member (7) is mounted in said plug (BM).

13. The engine system (SM) according to one of claims 6 to 8, wherein the second measuring member (7) comprises a temperature sensor mounted in a circulation duct of the lubrication circuit (5).

14. An aircraft comprising at least one engine system (SM) according to one of claims 6 to 13.