The invention relates to the monitoring of the state of health of a twin-body turbomachine of an aircraft and more particularly by means of the monitoring of vibration levels in the turbomachine. And the invention even more particularly the monitoring of the vibration sensors used for this purpose.

STATE OF THE ART

The state of health of a turbomachine is conventionally monitored by all kinds of sensors. Among them, the vibration sensors are essential because they make it possible to quickly detect a breakage of a part, an increase in clearance and any other failure that could endanger the turbomachine.

A double-body turbomachine conventionally comprises, in the direction of circulation of the air flow, a fan, a low-pressure compressor, a high-pressure compressor, a combustion chamber, a high-pressure turbine and a low-pressure turbine.

A known solution for monitoring the vibrations of the turbomachine is to position a vibratory sensor at the front of the turbomachine and another vibratory sensor at the rear of the turbomachine.

Each of these sensors, thus positioned, makes it possible to monitor the low pressure and high pressure vibration levels (that is to say of the low pressure body and of the high pressure body of the turbomachine) by means of filters controlled on the low pressure and high pressure regimes.

In order to guarantee the reliability of this monitoring of the vibration levels, it is necessary to ensure that the vibration sensors are functioning correctly in order to immediately bring up abnormal vibration levels of the turbomachine.

To perform this check, it is known practice to monitor the state of health of the vibration sensors on a criterion of stability of the vibration levels detected during the take-off and post-flight phases.

However, such a detection logic has limits, as false failures of the vibration sensors are declared wrongly.

The monitoring phases are not optimal, the vibration levels in these phases are often below the levels of detection of a failure of a sensor;

During operation at high temperature, the speed of the turbomachine being higher than during operation at nominal temperature, this may suggest that it is in a monitoring phase, the levels are then not recorded during the planned phase all the more so since they can also be below the levels of detection of a failure of a sensor.

PRESENTATION OF THE INVENTION

At least one aim of the invention is to define a fault detection logic for vibratory sensors with the aim of ensuring that only the really faulty sensors are declared as such.

To achieve this aim, the invention relates to a method for monitoring the state of health of at least two vibration sensors of a double-body turbomachine comprising a low-pressure body and a high-pressure body, a vibration sensor being located at the front of the turbomachine, a vibration sensor being located at the rear of the turbomachine, each of the sensors being configured to measure vibrations of the low pressure and high pressure bodies at the front and at the rear of the turbomachine, the method being implemented in a turbomachine processing unit (20) in communication with each of the sensors and comprising the following steps:

- reception of the low pressure (NBP) and high pressure (NHP) speeds of the turbomachine and when said speeds are simultaneously in predetermined ranges,

- reception of the front and rear vibration levels of the low and high pressure bodies recorded by each sensor;

- determination of the average of the values ​​of the vibration levels of the low and high pressure bodies received over a predetermined reception period;

determining the state of health of said at least first and second vibration sensors from a comparison of the average values ​​of the vibration levels of the low and high pressure bodies determined at predetermined thresholds.

The invention is advantageously completed by the following characteristics, taken alone or in any of their technically possible combination.

The method comprises, during the reception step, a step of verifying the low pressure and high pressure regimes, the method comprising an interruption of the reception of the vibration levels by the processing unit if the regimes are not simultaneously in the modes. predetermined ranges.

The determined average is an average of the values ​​of the vibratory levels of the low and high pressure bodies received determined for a number of values ​​received which corresponds to the predetermined reception duration, the average being able to be determined instantaneously during reception.

The method monitoring two sensors two sensors, one sensor being configured to measure the vibration levels of the low pressure body and the high pressure body at the front of the turbomachine, the other being configured to measure the vibration levels of the low pressure body and of the high pressure body at the rear of the turbomachine, the state of health of a sensor being considered to be bad if the average values ​​of the vibration levels of the low pressure and high pressure bodies are below predetermined thresholds; and if for the other sensor the average values ​​of the vibration levels of the low pressure and high pressure bodies are greater than predetermined thresholds.

The method monitoring four sensors two sensors at the front of the turbomachine configured to respectively measure the vibration levels of the low pressure and high pressure bodies at the front, two sensors at the rear of the turbomachine configured to respectively measure the levels of vibrations of the low pressure and high pressure bodies at the rear, the state of health of a sensor of the vibration levels of the low pressure body being considered poor if the average value of the vibration levels is below a predetermined threshold, and if for the other sensor the average value of the vibration levels is greater than a predetermined threshold;the state of health of a high pressure body vibration level sensor being considered bad if the average value of the vibration levels is below a predetermined threshold, and if for the other sensor the average value of the vibration levels is greater than a predetermined threshold.

The method comprises confirming the good or bad state of health of a sensor when the sensor exhibits the same state of health three times consecutively.

By way of example, a predetermined vibratory threshold for the low pressure body is between 0.1 and 0.2 cm / s, typically 0.16 cm / s.

By way of example, a predetermined vibratory threshold for the high pressure body is between 0.05 and 0.15 cm / s, typically 0.10 cm / s.

The predetermined range for the low pressure speed is between 10,500 rpm and 13,500 rpm and in which the predetermined range for the high pressure speed is between 14,500 rpm and 17500 rpm.

The invention also relates to a double-body turbomachine comprising a processing unit configured to implement a method according to the invention.

The advantages of the invention are numerous.

The detection of faults is more robust than by means of known solutions. Indeed, the detection is done at higher speeds (therefore more "vibrating") and the need to confirm the calculation of the averages several times also makes it possible to make the reality of the sensor failure more robust.

False failures are therefore limited.

It is possible to rehabilitate a sensor that has been declared faulty.

PRESENTATION OF FIGURES

Other characteristics, aims and advantages of the invention will emerge from the following description, which is purely illustrative and non-limiting, and which should be read with reference to the appended drawings in which:

[Fig. 1]

FIG. 1 schematically illustrates a double-body turbomachine,

[Fig. 2]

FIG. 2 illustrates an architecture for implementing the method according to the invention;

[Fig. 3]

FIG. 3 illustrates steps of a method according to the invention.

In all of the figures, similar elements bear identical references.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 illustrates a bypass and double-body turbomachine of an aircraft comprising, from upstream to downstream in the direction of the gas flow (along the engine axis AA), a ducted fan 1, an annular space d 'primary flow I and an annular secondary flow space II (secondary flow) delimited by an outer casing 2 and an internal hub 3. The turbomachine comprises in the primary flow I, a low pressure compressor 11, a high pressure compressor 12 , a combustion chamber 13, a high pressure turbine 14 and a low pressure turbine 15.

The turbomachine therefore comprises at the front and at the rear (in the direction of flow of the gases) a low pressure body and a high pressure body.

As mentioned, in the introduction, vibration sensors are arranged at the front and at the rear to measure vibrations of the low pressure and high pressure bodies.

As illustrated schematically in FIG. 2, according to one embodiment, a sensor C1 makes it possible to measure vibrations V1 BP, V1 HP of the low pressure and high pressure bodies at the front and a sensor C2 makes it possible to measure vibrations V2BP, V2HP low pressure and high pressure bodies at the rear.

According to this embodiment, a single sensor is arranged at the rear and a single sensor is arranged at the front, each measuring both the vibrations of the low pressure and high pressure bodies. To do this, a filtering of the vibrations received must be carried out in order to be able to separate vibrations originating from the low pressure body from those originating from the high pressure body.

As a variant, four sensors can be provided, two at the front and two at the rear. In this variant, a C1 1 sensor makes it possible to measure V1 BP vibrations of the low pressure body at the front, a C12 sensor makes it possible to measure V1 HP vibrations of the high pressure body at the front, a C21 sensor makes it possible to measure vibrations V2BP of the low pressure body at the rear A C22 sensor is used to measure V2HP vibrations of the high pressure body at the rear.

Such vibration sensors are for example constituted by accelerometers.

The sensors can be positioned at several locations on the turbomachine. For example, to measure the vibrations at the front of the bass body

pressure, a sensor can be placed at the low pressure compressor. To measure the vibrations in front of the high pressure body, a sensor can be placed at the high pressure compressor. To measure the vibrations behind the high pressure body, a sensor can be placed at the high pressure turbine. To measure the vibrations at the rear of the low pressure body, a sensor can be placed at the level of the low pressure turbine.

As mentioned in the introduction, these vibration sensors need to be monitored. Such monitoring is implemented in a processing unit 20 by means of a method for monitoring the state of health of the vibration sensors described below in relation to FIG. 3.

The monitoring of the health of the vibration sensors is based on the exploitation of vibration measurements from the sensors in the low pressure and high pressure ranges for which the vibration levels are relevant.

Advantageously, the vibration levels are recorded, for monitoring, during periods T. This period T must be high enough to have an average of the vibration level measurements high enough (in the case of an integrated sensor) and therefore be above the detection threshold of a faulty sensor. Indeed, statistically, the longer the averaging time, the higher the calculated average will have. This period T must also be low enough to allow the system to be in the detection ranges long enough to ensure at least 3 averaging during a flight. This period is preferably between 60 and 120 s and preferably is equal to 90 s.

At the start of the method, the calculation step n is initialized at n = 0 (step E0) and the duration t = n.At is calculated (step E1) with At the duration of a recording of the vibration levels.

After these various initializations, the processing unit 20 receives E2 the low pressure NBP and high pressure NHP regimes and when these regimes are simultaneously in predetermined ranges, the processing unit 20 receives (step E3) vibratory levels V1 BP, V2BP, V1 HP, V2HP from the vibration sensors to be monitored.

The ranges of the low pressure NBP and high pressure NHP regimes are preferably as follows:

- NBP = [10500; 13500] rpm;

- NHP = [14500; 17500] rpm.

Such speeds are for example determined by a statistical study of the vibration levels actually seen by the engine at different speeds. The monitoring logic regimes are therefore chosen as a function of the vibratory values ​​with respect to the threshold and / or the threshold is chosen as a function of the relevance of the regimes resulting from the statistical study.

In the case of two sensors, one at the front, one at the rear, each sensor C1, C2 acquires two vibration levels:

- The C1 sensor at the front acquires low pressure vibration levels

V1 BP and high pressure V1 HP;

The C2 sensor at the rear acquires the low pressure V2BP and high pressure V2HP vibration levels.

In the case of four sensors, two at the front, two at the rear, each sensor C11, C12, C21, C22 acquires a vibration level:

The sensor C11 at the front acquires the vibration levels V1 BP of the front low pressure body;

The C12 sensor at the front acquires the V1 HP vibration levels of the high pressure body;

- The C21 sensor at the rear acquires the V2BP vibration levels of the low pressure body;

The C22 sensor at the rear acquires the V2HP vibration levels of the high pressure body.

From the values ​​received, the processing unit 20 calculates (step E4) the instantaneous average of each vibratory level as follows:

with i = {1, 2) and J = {BP, HP}.

The instantaneous average is calculated at each step n over the period T and at each calculation step n is incremented by 1 (step E8). At the end of period T, the averages

M1 BP, M1 HP of the levels of the low pressure and high pressure bodies measured by the front sensor (s);

M2BP, M2HP of the levels of the low pressure and high pressure bodies measured by the rear sensor (s);

are obtained.

Alternatively, the average can be calculated after all the values ​​of the vibration levels are acquired for a total time T. This means that the values ​​are stored as they are done.

In a complementary manner, in order to ensure that the low and high pressure regimes are indeed simultaneously within the predetermined ranges, the processing unit 20 checks (step E2) before each reception of the vibration levels, the values ​​of the low and high pressure regimes. . If this is not the case, the processing unit 20 interrupts (INT) (step E9) the reception of the vibration levels for the calculation of the average. On the other hand, as soon as the regimes return to the predetermined ranges, the processing unit 20 resumes where it left off.

When an averaged number of vibration levels corresponds to a period T = 90s (step E5) the processing unit 20 determines (step E6) the state of health of each sensor.

The state of health of a sensor is obtained from a comparison of each average M1 BP, M1 HP, M2BP, M2H with a vibratory threshold.

The low pressure threshold SBP is typically between 0.1 and 0.2 cm / s, preferably 0.16 cm / s

The high pressure threshold SHP is typically between 0.05 and 0.15 cm / s, preferably 0.10 cm / s.

Here again, these different thresholds come from a statistical study.

In the case of two sensors, the state of health ESij of a sensor is considered to be bad if the average values ​​of the vibration levels of the low pressure and high pressure bodies are below the thresholds SBP, SHP respectively; and if for the other sensor the average values ​​of the vibration levels of the low pressure and high pressure bodies are greater than the SBP and SHP thresholds respectively.

Alternatively, in the case of four sensors, the state of health ESij of a low pressure body vibration level sensor is considered poor if the average value of the vibration levels is below the SBP threshold, and if for the other sensor the average value of the vibration levels of the low pressure body is greater than the SBP threshold; the state of health of a high pressure body vibration level sensor is considered poor if the average value of the high pressure body vibration levels is below the SHP threshold, and if for the other sensor the average value of the vibration levels of the high pressure body is greater than the SHP threshold.

From the state of health thus determined, the processing unit 20 proceeds to a confirmation (step E7) of the state of health of the good or bad state of health of a sensor as soon as the sensor presents the same state of health three times consecutively.

It is therefore possible to rehabilitate a sensor whose state of health has been confirmed as bad.

WE CLAIMS

1. ​Method for monitoring the state of health of at least two vibration sensors of a double-body turbomachine comprising a low-pressure body and a high-pressure body, a vibration sensor (C1, C1 ') being located at the front of the turbomachine, a vibration sensor (C2, C2 ') being located at the rear of the turbomachine, each of the sensors being configured to measure vibrations of the low-pressure and high-pressure bodies at the front and to the rear of the turbomachine​, the method being implemented in a processing unit (20) of the turbomachine in communication with each of the sensors and comprising the following steps:

​-receiving (E1) low-pressure (NBP) and high-pressure (NHP) regimes of the turbomachine and when said regimes are simultaneously in predetermined ranges,

​-receiving (E3) the vibration levels (v1_BP, v1_HP, v2_BP, v2_HP, v3_HP, v3_BP) before and behind the low and high pressure bodies recorded by each sensor;

​-determining (E4) the average of the values of the vibration levels of the low and high pressure bodies received over a predetermined reception duration;

​-determining (E6) the state of health of said at least first and second vibration sensors from a comparison of the mean values of the vibration levels of the low and high pressure bodies determined at predetermined thresholds.

2. ​The method according to claim 1, comprising in the receiving step, a step of checking (E2) the low-pressure and high-pressure regimes, the method comprising an interruption (E9) of receiving the vibration levels by the processing unit if the regimes are not simultaneously within the predetermined ranges.

3. ​Method according to one of the preceding claims, in which the determined average (E4) is an average of the values of the vibration levels of the received low and high pressure bodies determined for a number of received values which corresponds to the predetermined reception duration, the average being able to be determined instantaneously during the reception.

4. ​The method of claim 1, comprising two sensors (C1, C2), one sensor being configured to measure the vibration levels of the low pressure body and the high pressure body at the front of the turbomachine, the other being configured to measure the vibration levels of the low pressure body and the high pressure body at the rear of the turbomachine​, the state of health of a sensor being considered bad if the average values of the vibration levels of the low-pressure and high-pressure bodies are lower than predetermined thresholds; and if for the other sensor the average values of the vibration levels of the low-pressure and high-pressure bodies are greater than predetermined thresholds.

5. ​The method according to claim 1, comprising four sensors (C1 1, C12, C21, C22), two sensors at the front of the turbomachine configured to respectively measure the vibration levels of the low-pressure and high-pressure bodies at the front, two sensors at the rear of the turbomachine configured to respectively measure the vibration levels of the low-pressure and high-pressure bodies at the rear​, the state of health of a sensor of the vibration levels of the low-pressure body being considered bad if the average value of the vibration levels is less than a predetermined threshold, and if for the other sensor the average value of the vibration levels is greater than a predetermined threshold; the state of health of a sensor of the vibration levels of the high-pressure body being considered bad if the average value of the vibration levels is less than a predetermined threshold​, and if for the other sensor the average value of the vibration levels is greater than a predetermined threshold.

6. ​Method according to one of the preceding claims, comprising a confirmation (E7) of the correct or bad state of health of a sensor as soon as the sensor has the same state of health three times consecutively.

7. Procédé selon l’une des revendications précédentes, dans lequel un seuil vibratoire prédéterminé pour le corps basse pression est compris entre 0,1 et 0,2 cm/s, typiquement 0,16 cm/s.

8. Procédé selon l’une des revendications précédentes, dans lequel un seuil vibratoire prédéterminé pour le corps haute pression est compris entre 0,05 et 0,15 cm/s, typiquement 0,10 cm/s.

9. Procédé selon l’une des revendications précédentes, dans lequel la plage prédéterminée pour le régime basse pression est entre 10500 tr/min et 13500 tr/min et dans lequel la plage prédéterminée pour le régime haute pression est entre 14500 tr/min et 17500 tr/min.

10. Turbomachine à double corps comprenant une unité (20) de traitement configurée pour mettre en oeuvre un procédé selon l’une des revendications précédentes.