Turbomachine monitoring method

Abstract

The invention relates to a method for monitoring a turbomachine comprising a duct through which an airflow circulates, said method comprising the steps of: recording sounds emitted by a wall (11, 12) of the duct during impacts on said wall (11, 12) of foreign bodies carried by the airflow and ingested into the duct, and detecting, in said recording, an acoustic signature representative of a type of impact on said wall (11). Figure for the abstract: Fig 2

Description

Title of the invention: Method for monitoring a turbomachine Technical field

[0001] The field of the invention is that of aircraft turbomachines, and more particularly that of two- or three-flow turbomachines. The invention more particularly proposes a method for monitoring the ingestion of foreign bodies in a vein of a turbomachine. State of the art

[0002] The air entering turbomachines may contain foreign bodies, hereinafter referred to as FOD, an acronym for the English expression "Foreign Object Damage". These foreign bodies may present a risk of damage to the internal elements of the turbomachine, or even obstruct air passages. These foreign bodies include water droplets and hail, crystals forming from water droplets, sand and birds. In open-fan turbomachines, the shape of the cone and the vein may lead to the ingestion of such bodies in small quantities into the central core.

[0003] It is desirable to detect the type and quantity of ingestions in order to warn the pilot of a possible risk, to control the evacuation of ingestions by one or more discharge valves (VBV, acronym for “Variable Bleed Valve”), to activate an increase in the propeller rotation speed and / or to trigger anti-icing protection steps.

[0004] It is also desired to estimate possible damage and / or obstruction of air passages due to ingestions and impacts received by the engine during a flight. Such an estimation makes it possible to schedule maintenance checks based on the engine's exposure to such attacks.

[0005] Typically, water ingestion and icing are determined by varying the thermodynamic parameters measured in the high-pressure compressor. In current turbomachines having a primary stream with one or more curvatures, and in some cases a double or triple-flow architecture, ingestions into the engine are in small quantities and therefore have little impact on the thermodynamic parameters. These small quantities of ingestion can, however, cause damage and therefore require detection and characterization depending on the type and size of the object ingested.

[0006] In addition, ingestion and freezing of ingested water quantities can occur in areas with complex geometry. This geometry impacts the air flow and the amount of water entering these areas. In such machines, the measurement of the variation of thermodynamic parameters in the high-pressure compressor is imprecise and difficult or even impossible to apply. In addition, a measurement of thermodynamic parameters does not provide information on the type of ingestion and does not allow to determine for example the quantity of a specific ingestion such as hail and the size of the ingested objects. Statement of the invention

[0007] An aim of the invention is to provide a method for monitoring the ingestion of objects such as ice crystals, sand or dust particles, hail or water droplets, in a turbomachine vein, a method suitable for a turbomachine having a double or triple flow architecture.

[0008] To this end, the invention proposes a method for monitoring a turbomachine comprising a vein in which an air flow circulates, said method comprising the steps consisting of: • to make a recording of sounds emitted by a wall of the vein during impacts on said wall of foreign bodies carried by the air flow and ingested into the vein, and • to detect, in said recording, an acoustic signature representative of a type of impact on said wall.

[0009] Preferably, the vein is a primary vein in which circulates an air flow intended for a combustion chamber of the turbomachine.

[0010] Advantageously, said recording is carried out by at least one sensor arranged in a ballistic impact zone of the wall exposed to direct impacts of objects ingested in the vein and / or in a rebound impact zone exposed to rebound impacts of objects ingested in the vein.

[0011] The recording of sounds can be carried out at a frequency between 50 Hz and 10 MHz.

[0012] Advantageously, the method further comprises a step of comparing the acoustic signature with a list of reference acoustic signatures and, based on this comparison, determining a type of object ingested into the vein.

[0013] Preferably, the method further comprises a step of determining, based on the comparison, the quantity of objects ingested into the vein.

[0014] Advantageously, the method further comprises a step of opening at least one discharge valve in a wall of the vein as a function of the detected acoustic signature.

[0015] The method may further comprise a step of modifying a speed of a low-pressure turbine of the turbomachine as a function of the acoustic signature. detected.

[0016] The method may further comprise a step of bypassing or activating a heat exchanger or a step of activating an anti-icing protection system based on the detected acoustic signature.

[0017] The invention also relates to a turbomachine for an aircraft comprising at least one sensor configured to record sounds emitted by a wall of a vein in which an air flow circulates during impacts on said wall of foreign bodies carried by the air flow.

[0018] The invention also relates to an aircraft, comprising a turbomachine as described above and a control system comprising a sound recorder, said control system being configured to determine, in the recorded sound, an acoustic signature representative of a type of impact on a wall of a vein of the turbomachine. Brief description of the figures

[0019] Other characteristics and advantages of the invention will emerge from the detailed description which follows, with reference to the appended drawings, in which:

[0020] [Fig. 1] is a partial sectional view of a dual-flow turbomachine comprising a curved primary vein.

[0021] [Fig.2] is a detailed view of the primary vein of [Fig.l].

[0022] [Fig.3] illustrates the ballistic impact and rebound zones of the primary vein of [Fig.2],

[0023] [Fig.4] illustrates the steps of the monitoring method. Detailed description of embodiments

[0024] In the following description, the terms "internal" and "external" refer to a positioning relative to the longitudinal axis of rotation of a turbomachine. The axial direction corresponds to the direction along the longitudinal axis of rotation of the turbomachine. The radial direction is perpendicular to the longitudinal axis. The terms "front" and "rear" are to be understood in the direction of movement of the aircraft in flight. The terms "upstream" and "downstream" are to be understood in the direction of circulation of an air flow in a vein of the turbomachine.

[0025] [Fig.l] is a sectional view of an unducted aircraft turbomachine. The turbomachine comprises a gas turbine engine driving a fan arranged along a longitudinal axis X of the turbomachine. A primary duct V1 is used to convey a primary airflow which circulates in the gas turbine or primary body. The turbomachine may comprise other airflow ducts having a junction with the primary duct VI so as to divide the airflows. Generally, each duct is a fixed part, i.e. it is not rotating. during the operation of the turbomachine.

[0026] The vein V1 has a forward opening through which the air flow is conveyed. Typically, the vein has at least one bend or elbow C so that the inner portion of the vein is not directly exposed to the air currents coming from the blower. Only a portion of the vein located upstream of the elbow C in the direction of air circulation is directly exposed to the air currents.

[0027] Objects such as water droplets and hail, crystals forming from water droplets, sand and birds passing through said opening follow a ballistic trajectory. Thus, these objects can directly impact an area 20 close to the opening of the vein, upstream of the bend C in the direction of airflow and on the radially outer wall 11 of the vein. The objects can then rebound on said wall 11 and impact other areas of the same vein and / or the walls of other veins in the event of a division of the airflow into two (or more) veins. The areas impacted by rebounds can be located on the radially inner wall 12 or on the radially outer wall 11. The impacts can take place at the bend C, or before or after the bend C in the direction of airflow.

[0028] With reference to [Fig. 2], the vein V1 is equipped with one or more sensors C1, C2, C3, C7, C8 arranged on the walls 11, 12 of the vein. Alternatively, the sensors may be arranged in openings included in a wall, on a rear face of a wall, or in other locations close to the wall. The walls 11, 12 of the vein may be made of a material promoting the emergence and transmission of a sound during an impact, or may include a coating of such a material.

[0029] Each sensor C1, C2, C3, C7, C8 is an acoustic sensor adapted to detect a sound emitted by a wall of the vein during an impact of a foreign object on said wall. For example, a sensor may be a microphone or a piezoelectric sensor. Such an acoustic sensor preferably detects sounds having a frequency of the audible spectrum. For example, the sensor may be adapted to detect a sound in a frequency range between 1 Hz and 10 MHz, preferably between 50 Hz and 10 MHz. More specifically, the sensor may be adapted to detect a sound in a frequency range between 50 Hz and 1000 Hz to detect hail, in a frequency range between 0.1 MHz and 10 MHz to detect sand and / or a frequency range between 1 Hz and 10 Hz to detect bird debris or a whole bird.Such a frequency range allows for precise detection of noises emitted by objects impacting a wall of an aircraft vein and to distinguish noises according to the type and size of the object as well as the concentration of ingested objects.

[0030] The vein can be equipped with a single sensor, several identical sensors or several different sensors. With reference to [Fig. 3], one or more sensors C1, C2, C3 may be arranged in a ballistic impact zone 20.

[0031] The ballistic impact zone 20 can receive objects coming from outside the turbomachine following a ballistic trajectory T. Said ballistic impact zone 20 is located on the radially outer wall 12 relative to the longitudinal axis of rotation X and upstream of the elbow C. As illustrated in [Fig. 3], the ballistic impact zone 20 is defined by the outer trajectory Te in the direction of the front edge of the vein, and an inner trajectory T; corresponding to the maximum penetration into the vein V1 on a ballistic trajectory.

[0032] The sensors C1, C2, C3 arranged in the ballistic impact zone 20 are intended for the detection of a sound caused by the impact of an object coming from outside the vein and following an essentially ballistic trajectory T. Due to the high speed of objects coming from outside during a flight, such an object has a strong impact on the wall 12 of the vein. The first impact of each object being located in this zone 20, such an arrangement of the sensors C1, C2, C3 makes it possible to detect the impact of each object as soon as it is ingested into the vein VL.

[0033] Other sensors C7, C8, can be arranged in a rebound zone 40 which cannot be directly impacted by an object coming from outside the vein following a ballistic trajectory T. The rebound zone 40 therefore receives only objects which have undergone one or more rebounds on a wall 11, 12 of the vein VL. In the vein VI illustrated in [Fig.3], the rebound zone 40 covers a portion of the radially outer wall 11 of the vein at the bend C and downstream of the bend C, and the radially inner wall 12 of the vein.

[0034] The detection of impacts by rebound makes it possible to draw conclusions on the effective trajectory of each object within the vein and to better characterize the type and size of each object.

[0035] The precise positioning of the sensors in the ballistic zone and in the rebound zone can be determined by a trajectory analysis carried out before implementing the method according to the invention. Such an analysis makes it possible to determine one or more zones in which a sound can be detected under optimal conditions, for example a high sound level and / or a high impact frequency in the event of a multitude of ingestions of small objects.

[0036] The number of sensors depends on the number of casing arms which divide the stream into several angular sectors. The numbers of sensors indicated below are given per sector and must therefore be multiplied by the number of sectors to obtain the number of sensors in the turbomachine.

[0037] The number of sensors per sector is typically between one and four. Preferably, between one and four sensors are positioned in the ballistic impact zone. 20 and between one and four sensors in the rebound zone 40. The distance between two adjacent sensors is typically between 16 mm and 80 mm, which corresponds to the dimension of approximately one to five particle diameters to be detected. Such an arrangement allows good coverage of the vein V1 in order to detect all the impacts relevant for an accurate analysis.

[0038] The aircraft further comprises a control system in communication with one or more sound recorders. Each sensor is in communication with a sound recorder configured to record a sound from the respective sensor. The recording is used for analysis by the control system. The control system may be a system dedicated to the method according to the invention, or the computer system responsible for engine control (FADEC, acronym for the English term “Full Automatic Digital Engine Control”) of the aircraft. When the control system in communication with the sound recorder is a dedicated system, said system is preferably in communication with the FADEC.

[0039] The use of the FADEC as a control system makes it possible to use existing communication channels, and to communicate directly with other elements of the aircraft, for example to carry out the evacuation of ingested objects or de-icing in the event of water ingestion in a low temperature environment.

[0040] A dedicated control system can be arranged in a position optimized for sound processing. A dedicated control system can also be designed in a relatively simple manner.

[0041] The control system comprises software for comparing recorded acoustic signatures with a database. Said software can access a database of acoustic signatures. In the database, each acoustic signature is linked to one or more types of objects likely to be ingested in an air circulation vein. The comparison with the database thus makes it possible to determine a type of ingested object based on its acoustic signature.

[0042] Such a database may be established on the basis of measurements carried out during tests on an engine, a part of an aircraft or an aircraft on the ground. The database may also include acoustic signatures recorded on a turbomachine in service. The database may include data created by an artificial intelligence system taking into account local meteorological data for recordings of sounds coming from the sensors during a flight. The database may be supplemented and improved in terms of accuracy throughout its use.

[0043] The turbomachine further comprises a compressor comprising one or more variable discharge valves (VBV, an acronym for the term Variable Bleed Valve). Each variable discharge valve is configured to move between a closed position, in which circulation from the primary vein to other circulation veins is prohibited, and an open position in which circulation from the primary vein to one or more additional veins is permitted. In the open position, the variable discharge valves also allow the ejection of centrifuged debris present in the primary flow. Said discharge valves can be used to evacuate one or more ingested objects, or for example to evacuate water after defrosting or the melting of ingested hailstones.

[0044] The dump valves are typically controlled by the computer system responsible for controlling the aircraft engines (FADEC). The dump valves may be controlled based on a parameter transmitted by the control system in communication with a sound recorder. For example, the degree of opening of one or more dump valves may be controlled based on a type and / or quantity of ingested objects, said type and quantity being determined by comparing their acoustic signatures with the database.

[0045] The turbomachine typically comprises in the primary vein VI, a low-pressure compressor, a high-pressure compressor, a combustion chamber, a high-pressure turbine and a low-pressure turbine in the case of a twin-spool, twin-flow engine. In the case of a triple-spool architecture, the turbomachine further comprises an intermediate compressor and an intermediate turbine. When one or more objects are ingested, it may be necessary to modify the speed of the low-pressure turbine and / or the intermediate turbine in order to protect said turbine. For example, the speed of said turbine may be lowered in order to avoid too violent an impact with an ingested object.

[0046] The rotational speed of the low-pressure turbine is controlled by the computer system responsible for controlling the aircraft engines (FADEC). Said rotational speed can be controlled according to a parameter transmitted by the control system in communication with a sound recorder. For example, the rotational speed of the low-pressure turbine is lowered according to a type and / or a quantity of ingested objects, said type and said quantity being determined by comparing their acoustic signatures with the database.

[0047] The aircraft typically comprises an ice protection system. Such an ice protection system may comprise a heating mat arranged on one or more surfaces of the aircraft and / or inside the turbomachine, or another system adapted to heat one or more surfaces in order to melt hailstones and / or layers of ice forming when the quantities of water present on these surfaces freeze. Typically, the ice protection system is activated and controlled by the computer system responsible for controlling the aircraft engines (FADEC). Said ice protection system may be controlled according to a parameter transmitted by the control system in communication with a sound recorder. For example, the ice protection system is activated or the temperature of such a system is adapted according to a type and / or quantity of ingested objects, for example rain or hail. Said type and quantity of ingested objects are determined by comparing their acoustic signatures with the database.

[0048] A method for monitoring a turbomachine will now be described. When the turbomachine is in operation, an air flow from outside the turbomachine is conveyed through the primary stream. This air flow is typically conveyed to a combustion chamber.

[0049] The air flow can carry foreign bodies, i.e. objects of different types and sizes, for example rain or fog droplets, hailstones, sand, birds or other. Each object typically follows a ballistic trajectory T and can directly impact the ballistic impact zone 20 on the inner wall 11 of the vein VL. Upon impact in this zone 20, the wall 11 emits a sound caused by the beating of the object on the wall 11. Each sound has a specific acoustic signature with several parameters such as the frequencies included in the sound, their respective intensity and their temporal evolution. The acoustic signature of an impact typically depends on the size, geometry and hardness of the object. The acoustic signature can also depend on the temperature of an object, its surface condition and the speed of the object relative to the wall of the vein.

[0050] For example, the acoustic signature of a liquid water droplet is different from the acoustic signature of a hailstone, even if the amount of water in the droplet and in the hailstone are identical. Similarly, the signature of a hailstone and a grain of sand having the same size or mass are typically different.

[0051] In the case of a plurality of objects, a plurality of sounds are emitted in a superimposed manner. In this case, the noise emitted by the wall may comprise a combination of sounds emitted simultaneously or successively, or having a temporal overlap. An acoustic signature may also comprise parameters such as the density and temporal overlap of such sounds.

[0052] Each object can rebound following its first impact on the wall 11 of the vein VI, and impact a second zone 40 of the vein VL. In this second zone 40, the impact of the rebounded object causes a second sound having an acoustic signature which may be different from the first acoustic signature. In addition, the trajectory of the rebounded object and its speed also depend on the type and size of the object. The impact and force of the rebound also depend on the type and size of the object. The object can undergo multiple rebounds, causing multiple sounds at different different positions of the vein wall. Generally, the object moves in the direction of the airflow during multiple bounces. This movement and the evolution of the position and acoustic signature of each bounce can be characteristic for a type of ingested object and depend on the size and other parameters of such an object.

[0053] The steps of the monitoring method are illustrated in [Fig.4].

[0054] During step 1, each sound emitted by the walls 11, 12 of the vein V1 is detected by one or more sensors C1, C2, C3, C7, C8. During the first impact of an object coming from outside the vein, a sound is detected by the sensors C1, C2, C3 arranged at the ballistic impact zone 20. In the case of a sound having a high volume, sensors C7, C8 arranged in other areas of the vein can also detect this sound. The sound detected by the sensors C7, C8 far from the ballistic impact zone is generally weaker and can be distorted. In addition, the sound can be reflected on the walls and cause an echo which will also be detected by the sensors C1, C2, C3, C7, C8.

[0055] Sounds emitted following rebounds cause sounds emitted by other portions of the vein wall. Sensors C7, C8 arranged near the area of ​​each respective impact detect the highest volume of the impact in question. Sensors further away from the impact in question detect a lower sound which may be distorted. Typically, some sensors very far from the impact area in question do not detect any sound for such an impact.

[0056] During step 2, the sound is recorded by a sound recorder in communication with each sensor.

[0057] During step 3, an analysis of each recorded sound is carried out to detect a specific acoustic signature of the sound via a control system in communication with the sound recorder. The control system analyzes parameters such as the intensity, frequency distribution and duration of each sound, and the sequence of consecutive impacts. The control system may also analyze the distribution of sound elements in the case of several sensors and / or effects such as the distortion of the sound propagating in the vein and the echoes produced by the reflection of the sound on the walls of the vein.

[0058] The number of events, for example the number of impacts in the ballistic impact zone, can be determined. In the case of several simultaneous impacts, the signature and the volume of the acoustic signature are modified. In the case of a very large quantity of objects, for example a cloud of hailstones or water drops, it may be impossible to detect the impact of individual objects, but a signature of a set of objects. Illustratively and not limitingly, a cloud of hailstones can cause a sound of several tens of decibels in which the sound emitted by a specific hailstone cannot be isolated. In this case, the duration, intensity and variation of the sound in- recorded are also considered as an acoustic signature.

[0059] During step 4, an evaluation of the detected acoustic signatures is carried out. Typically, the control system compares each acoustic signature detected by each sensor with a database containing acoustic signatures for different types and sizes of objects. This makes it possible to identify, during step 5, the type of an ingested object by the acoustic signatures detected by one or more sensors. In this step, the number and / or density of ingested objects is also determined. The information on the number of objects typically depends on the frequency of impacts and the number of sounds.

[0060] Combinations of acoustic signatures for several sensors arranged in the same or different impact zones can be analyzed. Such analysis of combinations makes it possible to improve the accuracy of the information on the type and number of objects ingested in the vein.

[0061] The duration and intensity of the recorded sound are also analyzed. For example, the duration of a characteristic sound for a cloud of objects such as hailstones or water droplets makes it possible to determine the time during which the aircraft passed through the cloud of hail or droplets, and, depending on the speed of the aircraft, the size of the cloud.

[0062] Following the evaluation of the detected acoustic signatures, information is now available on the type of object(s) ingested into the vein and their quantity. The control system can be used to analyze this information together with other data such as the outside temperature, the speed of the aircraft and the altitude in order to determine a state of the turbomachine and any actions to be triggered.

[0063] In step 6, the information obtained on the ingested object(s) can be used to control one or more measures to evacuate one or more objects and / or to limit damage that may be caused by the object ingested in the turbomachine.

[0064] For example, the control system may determine, based on temperature and an amount of ingested water, a risk of frost formation. In this case, the control system may trigger an activation of an ice protection system and / or adjust the temperature and other parameters of the ice protection system.

[0065] In other cases, where there is a risk of freezing or icing or, conversely, the risk of excessively high temperatures following impacts, the activation of a heat exchanger or a bypass of such an exchanger can be controlled by the control system.

[0066] In another example, the control system may determine an amount of water, sand, or other objects ingested into the vein, requiring discharge through the variable discharge valves. Depending on the type and / or amount of the ingested objects, the control system may trigger the partial or total opening of one or more discharge valves. This optimizes the evacuation of ingested objects, limiting the impact on airflow to a minimum for such evacuation.

[0067] In the case of one or more impacts presenting a risk of damage to the low-pressure turbine, the rotational speed of the low-pressure turbine can be modified via the control system, for example by reducing the rotation speed for a predefined time or a time determined according to the acoustic signature of the ingested object.

[0068] Measures adapted to the type and quantity of ingestions make it possible to optimize evacuation, defrosting and any other approach while minimizing the impact on the air flow in the vein and the operation of the turbomachine.

[0069] The recorded acoustic data and signatures can also be used in the context of aircraft maintenance planning. For example, in the case of specific ingestions such as sand, or strong impacts, the planning of shortened maintenance intervals can be triggered. These maintenance intervals can be specific for the parts of the aircraft concerned by the determined ingested object, for example the rotor and the low-pressure turbine.

Claims

Claims

1. Method for monitoring a turbomachine comprising a vein in which an air flow circulates, said method comprising the steps consisting of: • making a recording of sounds emitted by a wall (11, 12) of the vein during impacts on said wall (11, 12) of foreign bodies carried by the air flow and ingested into the vein, and • detecting, in said recording, an acoustic signature representative of a type of impact on said wall (11).

2. Method according to claim 1, in which the vein is a primary vein (VI) in which circulates an air flow intended for a combustion chamber of the turbomachine.

3. Method according to claim 1 or claim 2, wherein said recording is carried out by at least one sensor (C1, C2, C3) arranged in a ballistic impact zone (20) of the wall exposed to direct impacts of objects ingested in the vein and / or in a rebound impact zone (40) exposed to rebound impacts of objects ingested in the vein.

4. A method according to any one of claims 1 to 3, wherein the recording of sounds is carried out at a frequency between 50 Hz and 10 MHz.

5. A method according to any one of claims 1 to 4, further comprising a step of comparing the acoustic signature with a list of reference acoustic signatures and, based on this comparison, determining a type of object ingested into the vein.

6. The method of claim 5, further comprising a step of determining, based on the comparison, the amount of objects ingested into the vein.

7. A method according to any one of claims 1 to 6, further comprising a step of opening at least one discharge valve in a wall of the vein as a function of the detected acoustic signature.

8. Method according to any one of claims 1 to 7, further comprising a step of modifying a speed of a low pressure turbine of the turbomachine as a function of the detected acoustic signature.

9. A method according to any one of claims 1 to 8, further comprising a step of bypassing or activating a heat exchanger or a step of activating an ice protection system based on the detected acoustic signature.

10. Turbomachine for aircraft comprising at least one sensor (Cl, C2, C3, C7, C8) configured to detect sounds emitted by a wall (11) of a vein in which a flow of air circulates during impacts on said wall (11) of foreign bodies carried by the flow of air.

11. Aircraft, comprising a turbomachine according to claim 10 and a control system comprising a sound recorder in communication with at least one sensor (C1, C2, C3, C7, C8), said control system being configured to determine, in the recorded sound, an acoustic signature representative of a type of impact on a wall of a vein of the turbomachine.

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