Method for measuring the deformation of rotor blades of a turbomachine and associated turbomachine

Abstract

This method for measuring the deformation of blades (18) of a turbomachine rotor (2) comprises: - calculating the differences between blade passage times (18) measured by radially external sensors (22) and blade passage times (18) measured by at least one radially internal sensor (20), which are the passage times closest to the blade passage times (18) measured by the radially external sensors (22) considered; and - using the calculated differences in a model to deduce the dynamic deflections of the blades (18). Figure for the abstract: Fig 2

Description

Title of the invention: Method for measuring the deformation of rotor blades of a turbomachine and associated turbomachine technical field

[0001] The invention relates technically to turbomachinery for aircraft.

[0002] In particular, the invention relates to a method for measuring the deformation of blades of a rotor of a turbomachine and a turbomachine including a computer configured to implement such a process. Previous techniques

[0003] During the design, verification, and validation of a turbomachine, it is necessary to experimentally characterize the vibrational behavior of the rotating elements of the turbomachine.

[0004] For this purpose, dedicated tests are implemented, for example to experimentally characterize blade deformations.

[0005] A method for measuring blade deformations is known from the prior art, consisting of using strain gauges, for example sensors glued onto the blades, which are capable of measuring deformations by knowing a constitutive law of the material of the blades.

[0006] However, the integration of these strain gauges can disrupt the dynamic behavior of the turbomachine being characterized, as well as the aerodynamics of the airflow within the turbomachine. Furthermore, these strain gauges are not suitable for the temperatures present in certain stages of the turbomachine, particularly the temperatures present in the low-pressure turbine of the turbomachine.

[0007] Prior art non-intrusive measurements consisting of measuring the blade transit time at their tip, i.e., at their radially outermost end, the radial direction being orthogonal to the axis of rotation of the rotating elements of the turbomachine. Such measurements are known to those skilled in the art under the English term "Tip-Thning".

[0008] The time measurements in passing at the tip of the blade are not suitable for the blades of a low pressure turbine of the turbomachine which are each provided with a heel at their radially external end.

[0009] To circumvent this difficulty, edge-timing measurements can be taken at the leading or trailing edge of the blade. Such measurements are known to those skilled in the art as "edge-timing".

[0010] The "Tip-Timing" and "Edge-Timing" methods known in the prior art are generally characterized by deformation detectability thresholds on the order of 100 pm.

[0011] Another known method, consisting of measuring variations in the length of the blades along a radial axis to deduce vibrational modes of the blades, is described in FR-B-3 037 394. Description of the invention

[0012] The present invention aims to overcome all or part of the aforementioned problems and to provide a method for measuring the deformation of blades of a rotor of a turbomachine having a blade deformation detection threshold lower than known methods of the prior art.

[0013] The invention relates to a method for measuring the deformation of blades of a turbomachine rotor, the turbomachine comprising at least one radially internal sensor configured to perform blade transit time measurements from a radially internal measuring point, and a plurality of radially external sensors configured to perform blade transit time measurements from radially external measuring points having different azimuths, the distance between each radially external measuring point and an axis of rotation of the turbomachine being strictly greater than the distance between said radially internal measuring point and the axis of rotation of the turbomachine, the method comprising:

[0014] - the calculation, for each radially external sensor, for each blade, and for for each revolution made by the rotor, the difference between, on the one hand, the passage time of the blade in question measured by the radially external sensor in question at the revolution in question and, on the other hand, the passage time of one of the blades which is measured by said radially internal sensor or by one of the radially internal sensors and which is the passage time closest to said passage time of the blade in question measured by the radially external sensor in question at the revolution in question; and

[0015] - the use, in a model for each radially external sensor considered, for each blade considered, and for each turn considered, corresponding calculated differences to deduce dynamic deflections of the blades.

[0016] The static deflection of a turbomachine blade is the measure of the displacement or deformation of the blade under the effect of static forces that do not vary over time.

[0017] The dynamic deflection of the blade is the measure of the displacement or deformation of the blade under the effect of dynamic forces that vary over time, such as turbomachine vibrations or air pressure variations. Dynamic deflection takes into account the effects of temporal variations, such as than malfunctions in the turbomachine or resonance phenomena.

[0018] By using the corresponding calculated differences, a time related to the static deformations of the blades is eliminated and a time related to the dynamic deformations of the blades is measured.

[0019] Unlike prior art measurements of blade tip or edge passage time which use an estimation of blade passage time from a rotor rotation time and the number of blades, the method according to the invention uses the blade passage times measured by the or each radially internal sensor, thus reducing the detectability threshold of blade deformations, and therefore improving the accuracy of their measurement, compared to prior art measurements of blade tip or edge passage time.

[0020] The method for measuring the deformation of blades of a rotor of a turbomachine according to the invention is compatible with the measurements of tip-timing times of blades, known as "Tip-Timing", and with the measurements of edge-timing times of blades, known as "Edge-Timing".

[0021] According to a first design, each radially external sensor of the turbomachine is configured to perform blade tip passage time measurements. This method of measuring blade deformations is known to those skilled in the art as "Tip-Timing".

[0022] According to a second alternative design, each radially external sensor of the turbomachine is configured to perform blade passage time measurements at the blade trailing edge or blade leading edge. This method of measuring blade deformations is known to those skilled in the art as "Edge-Timing".

[0023] Advantageously, the turbomachine comprising a plurality of radially internal sensors configured to perform blade transit time measurements from radially internal measuring points having different azimuths, the method comprises:

[0024] - the calculation, for each radially external sensor, for each blade, and for for each revolution made by the rotor, the difference between, on the one hand, the passage time of the blade in question measured by the radially external sensor in question at the revolution in question and, on the other hand, the passage time of one of the blades which is measured by one of the radially internal sensors and which is the passage time closest to said passage time of the blade in question measured by the radially external sensor in question at the revolution in question; and

[0025] -1'use, in said modeling for each radially external sensor considered, for each blade considered, and for each turn considered, corresponding calculated differences to deduce dynamic deflections of the blades.

[0026] By using the passage time closest to said passage time of the blade considered measured by the radially external sensor considered on the lathe considered, the accuracy of measuring the deformations of the blades is further improved.

[0027] Advantageously, the turbomachine comprises the same number of radially internal sensors and radially external sensors.

[0028] Advantageously, the radially inner and outer sensors are arranged in pairs, the radially inner and outer sensors of each pair having the same azimuth.

[0029] Advantageously, said or each radially internal sensor is located at a radial distance from the axis of rotation of the turbomachine which is between 0% and 50% of a distance range which goes from a radial distance taken between the axis of rotation of the turbomachine and the foot of one of the blades whose passage time is measured, to a radial distance taken between the axis of rotation of the turbomachine and the top of one of the blades whose passage time is measured, in particular between 10% and 30% of said distance range.

[0030] Advantageously, each radially external sensor is located at a radial distance from the axis of rotation of the turbomachine which is between 50% and 100% of said distance range, in particular between 60% and 90% of said distance range.

[0031] Optionally, the method for measuring the deformation of blades of a rotor of a turbomachine includes prior numerical simulations, in particular by finite elements, to determine an inside radial distance corresponding to a blade vibration node, said or each radially inside sensor being located at said inside radial distance.

[0032] The vibration node of a blade corresponds to the radial position at which the blade in question does not vibrate, or to the radial position at which the blade in question is subject to a minimum of vibration.

[0033] Optionally, the method for measuring the deformation of blades of a rotor of a turbomachine includes prior numerical simulations, in particular by finite elements, to determine an outside radial distance corresponding to a blade vibration antinode, each radially outside sensor being located at said outside radial distance.

[0034] The antinode of vibration of a blade corresponds to the radial position at which the blade in question is subject to a maximum of vibrations.

[0035] Optionally, the method for measuring the deformation of blades of a rotor of a turbomachine includes the calculation of an instantaneous regime of the turbomachine as a function of the blade passage times measured by said or the radially internal sensor(s) and of angular positions of the rotor associated with them, said modeling including the use of the calculated instantaneous regime of the turbomachine to deduce the dynamic deflections of the blades.

[0036] The accuracy of calculating the turbomachine regime, and therefore the dynamic deflections of the blades, is thus improved compared to calculations carried out from measurements of time of passage at the tip or edge of the blade known from the prior art.

[0037] Preferably, the transit times measured by the radially internal and external sensors are measured cumulatively.

[0038] Optionally, the calculation of the instantaneous speed of the turbomachine includes:

[0039] - the formation of pairs of values, for said or each radially sensor internally, for each blade, and for each revolution made by the rotor, between, on the one hand, the passage time of the blade in question measured by the radially internal sensor in question at the revolution in question and, on the other hand, the associated angular position of the rotor which is measured cumulatively; and

[0040] - the ranking of all pairs of values ​​in ascending order of time passage measured by said internal radial sensors.

[0041] Such a classification allows for simplified manipulation of pairs of values. The cumulatively measured angular position of the rotor is not a modulo 2ir measurement and can take values ​​strictly greater than 360 degrees.

[0042] Optionally, the calculation of the instantaneous turbomachine speed Reg(t) is performed piecewise Regp(t), said calculation comprising, for any time t between two transit time values ​​ToaRp, ToaRp+ measured by said or the radially internal sensors which are successive in ascending order, the intermediate calculations of:

[0043] - RpoDF — [___'^2?^___j y 1 with the values ​​of the angular position of the \ ToaRp^-ToaRp y 6 rotor, measured in degrees, associated with the measured transit times ToaRp, ToaR^i, measured in seconds; and

[0044] - with Ne the number of radially internal sensors; Regp = ---2—”

[0045] to determine RegMoy-RegMoy. Regp(t) = T^^RP- (t-ToaRp) +Regpoy

[0046] Reg®F is expressed in revolutions per minute.

[0047] When the turbomachine includes several radially internal sensors, the accuracy of calculating the instantaneous speed is improved due to the higher number of measurement points used for this piecewise interpolation.

[0048] Advantageously, said modeling includes the use of a correction parameter for an azimuth offset between the radially outer sensor considered and the radially inner sensor which measures the passage time closest to the passage time of the blade considered at the turn considered.

[0049] Thus, the accuracy of said modeling is further improved.

[0050] Advantageously, said modeling includes the calculation of the dynamic deflections of the blades as:

[0051] Re^Toa.\ = 2æ ■ Radius ■ —• ( Toa^-Tref ) - Radius • + Z?)

[0052] in which i is the dawn considered;

[0053] j is the turn considered;

[0054] k is the radially external sensor considered;

[0055] Radius is the distance between the axis of rotation of the turbomachine and the radially external measuring point of the radially external sensor considered;

[0056] Reg(t) the instantaneous operating regime of the turbomachine;

[0057] Toai,j,k is the passage time of the considered blade measured by the radially external sensor considered at the considered lathe;

[0058]

[0059]

[0060]

[0061] Tref is the passage time of one of the blades, measured by the radially internal sensor or by one of the radially internal sensors, and is the passage time closest to the passage time of the blade in question, measured by the radially external sensor in question at the given revolution. We therefore obtain Tref = ToaR^'j'j, where l is the index of the radially internal sensor, which measures the passage time Tref of blade i' at revolution j'. y is the oriented angle between the radially external sensor considered and the radially internal sensor which measures the passage time closest to the passage time of the blade considered at the considered turn; [3 is a correction parameter for an azimuth offset between the radially outer sensor considered and the radially inner sensor that measures the transit time closest to the transit time of the blade considered at the considered revolution. [3 also corrects a dependence on the indices "i, i', j and j'" of the terms Toai jk and Tref for each calculation of a dynamic blade deflection lyjji For example, a gain of more than two orders of magnitude in the detectability threshold for blade deformations of the order of 40 pm has been observed, and another two and six orders of magnitude of improvement in the accuracy of blade deformation measurements.

[0062] In a particular embodiment, the method for measuring the deformation of blades of a rotor of a turbomachine is implemented by computer.

[0063] The present invention also relates to a computer program comprising code instructions which, when the program is executed by a computer, lead the computer to implement the process defined above.

[0064] The present invention also relates to a computer-readable data carrier on which a computer program as defined above is recorded.

[0065] The present invention also relates to a turbomachine comprising at least one radially internal sensor configured to perform blade passage time measurements from a radially internal measurement point, and a plurality of radially external sensors configured to perform blade passage time measurements from radially external measurement points having different azimuths, the distance between each radially external measurement point and an axis of rotation of the turbomachine being strictly greater than the distance between said radially internal measurement point and the axis of rotation of the turbomachine, the turbomachine further comprising a computer configured to implement the method of measuring the deformation of blades of a rotor of a turbomachine as defined above. Brief description of the drawings

[0066] Other objects, features and advantages of the invention will become apparent from the following description, given solely by way of non-limiting example and made with reference to the accompanying drawings in which:

[0067] [Fig-1] schematically illustrates a turbomachine equipped with a computer according to a example of the implementation of the invention;

[0068] [Fig.2] schematically illustrates radially external and internal sensors of the turbomachine of [Fig.1];

[0069] [Fig.3] schematically illustrates a dynamic deflection of a blade of the turbomachine of [Fig.1];

[0070] [Fig.4] illustrates in perspective a blade of a low-pressure turbine of the turbomachine of the [Fig. 1]; and

[0071] [Fig. 5] schematically illustrates a method for measuring the deformation of the blades of a turbomachine rotor according to an embodiment of the invention. Detailed description

[0072] Fig. 1 represents a turbomachine 2 with longitudinal axis X coinciding with an axis of rotation of the rotating elements of the turbomachine 2. The turbomachine 2 comprises, from upstream to downstream with reference to the direction of gas flow through the turbomachine 2, a blower 4, a low-pressure compressor 6, a high-pressure compressor 8, a combustion chamber 10, a high-pressure turbine 12, and a low-pressure turbine 14.

[0073] The turbomachine 2 further includes a computer 16 capable of implementing a method for measuring the deformation of the blades 18 of the turbomachine 2.

[0074] Figure 2 represents a rotating blade stage 18 of the turbomachine 2. The turbomachine 2 comprises a plurality of radially internal sensors 20 and a plurality of radially external sensors 22. More specifically, the radially internal and external sensors 20, 22 are arranged on a stator stage of the turbomachine 2 and measure the passage times of the blades 18 of a rotor stage of the turbomachine 2.

[0075] Each radially internal sensor 20 is capable of measuring the passage times of the blades 18 from a radially internal measuring point. The radially internal sensors 20 are arranged at different azimuths. All the radially internal sensors 20 are at the same radial distance from the axis of rotation of the turbomachine 2.

[0076] Each radially external sensor 22 is capable of measuring the passage times of the blades 18 from a radially external measuring point. The radially external sensors 22 are arranged at different azimuths. All the radially external sensors 22 are at the same radial distance from the axis of rotation of the turbomachine 2.

[0077] The radially external sensors 22 are strictly further from the axis of rotation of the turbomachine 2 than the radially internal sensors 20.

[0078] Each radially inner sensor 20 here has the same azimuth as one of the radially outer sensors 22. Alternatively, the radially inner sensors 20 and the radially outer sensors 22 could have different azimuths.

[0079] In the example shown, the turbomachine 2 comprises fewer radially internal sensors 20 than radially external sensors 22. Alternatively, the turbomachine 2 could comprise the same number of radially internal and external sensors 20, 22 or a greater number of radially internal sensors 20. In a variant, the turbomachine 2 could have only one radially internal sensor 20.

[0080] With reference to [Fig. 3], the moving blades 18 undergo deflections relative to their rest position 24. In particular, each moving blade 18 undergoes a tangential displacement of its radially outer end in reaction to vibrations of the turbomachine 2. These deflections can be broken down into a so-called static component which is generated by forces not varying over time, and a so-called dynamic component which is generated by forces which vary over time.

[0081] Figure 3 further shows a radially internal measurement point 26 located near a blade vibration node 18, a radially external measurement point for a blade edge measurement 28 located at a blade vibration antinode 18, and a radially external measurement point for a blade tip measurement 30. The radially external measurement point for a blade edge measurement 28 corresponds, for example, to a measurement known to those skilled in the art as "Edge-Timing." The radially external measurement point for a blade tip measurement corresponds, for example, to a measurement known to those skilled in the art as "Edge-Timing."

[0082] Preliminary numerical simulations, particularly using finite elements, can be performed to determine an inner radial distance corresponding to a blade vibration node 18 so as to place each radially inner sensor 20 at the inner radial distance from the axis of rotation. Similarly, preliminary numerical simulations, particularly using finite elements, can be performed to determine an outer radial distance corresponding to a blade vibration antinode 18 so as to place each radially outer sensor 22 at the outer radial distance from the axis of rotation.

[0083] Fig. 4 represents in perspective the blade 18 and radially external measurement points at the leading and trailing edges 28a, 28b.

[0084] Fig. 5 schematically represents the method for measuring the deformation of the blades 18 of the turbomachine 2.

[0085] We start with a step 32 during which measurements are taken, with the radially external sensors 22, of the Toa passage times of the blades 18 from radially external measurement points 28 or 30, and measurements are taken, with the radially internal sensors 20, of the ToaR passage times of the blades 18 from radially internal measurement points 26.

[0086] The turbomachine 2 includes an analog-to-digital converter (not shown) for converting the Toa and ToaR transit time measurements measured by the radially internal and external sensors 20, 22.

[0087] Then, in a step 34, the converted Toa and ToaR transit times, the angular positions of the radially external sensors 22, the angular positions of the radially internal sensors 20, the number of blades Na, the number of radially internal sensors Ne, and the angular deviations at between each blade 18 and a reference blade, hereafter referred to as aubei, are loaded along the direction circumferential of the turbomachine 2, of an angular deviation between the rotor reference frame and the stator reference frame co0, and of an angular deviation between the reference blade aubei and the stator a0. The angles are measured with respect to a reference direction R which is here vertical upwards.

[0088] Then, in a step 36, a calculation of the dynamic deflections of the blades 18 is carried out.

[0089] For this, we start with a sub-step 36a of calculating the angular positions of the rotor associated with the ToaR transit times measured by the radially internal sensors 20.

[0090] The calculation of the angular positions of the rotor is, for example, carried out in the following manner:

[0091] a), jj (rotor / stator) = m (rotor / blade 1) stator + m (blade 1 / blade) stator

[0092] + ai (aubei / stator)..,

[0093] In other words, the angle of the rotor relative to the stator which is associated with the measurement of the passage time ToaR for the blade i, at turn j and measured by the radially internal sensor 1 is equal to the sum of the angle between the reference frame of the rotor and the reference blade aubei, the angle between the blade i considered and the reference blade aubch and the angle of the blade i considered relative to the reference frame of the stator when it passes in front of the radially internal sensor 1 considered at turn j considered.

[0094] In particular, these terms are:

[0095] ai (aubei / stator) = + 360 • (j -1)

[0096] dawn! aubei) = 7^x(ï-1)

[0097] ai ( rot ! dawn 1 ) = a)0 -

[0098] Next, an indexing substep 36b is carried out in which pairs of values ​​are formed for each radially internal sensor 1, for each blade i, and for each revolution j made by the rotor, between, on the one hand, the passage time ToaRijj of the blade i considered measured by the radially internal sensor 1 considered at the revolution j considered and, on the other hand, the associated angular position of the rotor a)i,jj which is measured cumulatively, the angular position of the rotor being measured relative to the stator of the turbomachine 2. The passage times Toa, ToaR of the blades 18 are also measured cumulatively.

[0099] When the pairs of values ​​(ToaRijj ; cüijj) are formed, the set of pairs of values ​​is ranked in ascending order of the ToaRijj transit times measured by the radially internal sensors 20.

[0100] The pairs of values ​​(ToaRijj ; ranked are subsequently indexed (ToaRp ; a>p).

[0101]

[0102]

[0103]

[0104]

[0105]

[0106]

[0107]

[0108]

[0109]

[0110] Then, a sub-step 36c is carried out to calculate the instantaneous regime Reg(t) of the turbomachine 2 as a function of the passage times ToaRLJ of the blades 18 measured by the radially internal sensors 20 and the angular positions of the rotor associated with them, the calculation of the instantaneous regime Reg(t) including in particular the use of the pairs of classified and indexed values ​​(ToaRp; cop). The calculation of the instantaneous regime of the turbomachine Reg (t) is, for example, carried out by interpolation and piecewise Regp(t). To do this, during a first intermediate calculation, an approximation of the instantaneous regime is calculated by difference between two successive acquisitions Reg»F. For any time t between two transit time values ​​ToaRp, ToaRp+ measured by the radially internal sensors 20 which are successive in ascending order, we calculate: Regp — y ToaRp+i-ToaRp ) 6 With <J'p, les valeurs de la position angulaire du rotor, mesurées en degrés, associées aux temps de passage mesurés ToaRp, ToaRp+i, mesurés en secondes. Reg^F est exprimé en tours par minute. In a second intermediate calculation, a moving average of the approximations calculated in the first intermediate calculation is performed. In particular, we calculate. Regp - ---2~ The regime Reg(t) is then determined by piecewise interpolation: Ree^-Re»^ Regp(t) = ~ (t-ToaRp) + Regp '

[0111] A substep 36d of calculation, and optionally of correction, of dynamic deflections is then carried out.

[0112] During substep 36d, for each radially external sensor k, for each blade i, and for each revolution j made by the rotor, the difference is calculated between, on the one hand, the passage time Toal|k of the blade i considered measured by the radially external sensor k considered at the revolution j considered and, on the other hand, the passage time Tref of one of the blades i', at a revolution j', which is measured by one of the radially internal sensors 1 and which is the passage time ToaRple closest to said passage time Toaijjk of the blade i considered measured by the radially external sensor k considered at the revolution j considered.

[0113] In subsequent modeling, for each radially external sensor k considered, for each blade i considered, and for each turn j considered, the corresponding calculated differences are used to deduce dynamic deflections of the blades 18. These modelings include in particular the use of the instantaneous regime Reg(t) of the turbomachine.

[0114] Optionally, in each model, a correction parameter for the azimuth offset between the radially external sensor k considered and the radially internal sensor 1 is used, which measures the passage time Tref, also called ToaRi jj, closest to the passage time Toal|k of the blade i considered at the turn j considered.

[0115] In particular, each model includes the calculation of the dynamic deflections of the blades 18 as:

[0116]

[0117] RegiToa...) / \ = 2tt • Rayon •---■ ( Toa^-Tref ) - Rayon • + / 3]

[0118] With i the number of the blade 18 considered, j the revolution considered, k the radially external sensor 22 considered, Rayon the distance between the axis of rotation of the turbomachine 2 and the radially external measuring point 28, 30 of the radially external sensor 22 considered, Reg(t) the instantaneous speed of the turbomachine, Toaijjk the passage time of the blade i considered measured by the radially external sensor k considered at revolution j considered, Tref the passage time of one of the blades i' at revolution j which is measured by one of the radially internal sensors 1 and which is the passage time closest to said passage time Toaijk of the blade i considered measured by the radially external sensor k considered at revolution j considered, y the oriented angle, positive or negative,which is measured between the radially external sensor k considered and the radially internal sensor 1 which measures the passage time Tref closest to the passage time Toa^^ of the blade i considered at the considered revolution j, [3 the correction parameter for an azimuth offset between the radially external sensor k considered and the radially internal sensor 1 which measures the passage time Tref closest to the passage time Toa^k of the blade i considered at the considered revolution j. ,

[0119] Advantageously, the instantaneous regime of the turbomachine Reg(t) is calculated piecewise R&gp(t).

[0120] The parameter [3] for correcting an azimuth offset between the radially external sensor k considered and the radially internal sensor 1 which measures the passage time Tref closest to the passage time Toa^^ of the blade i considered at the revolution j considered is, for example, equal to:

[0121] p = [(ii )+Na-(jj)

[0122] With i' dawn 18 whose passage time Tref, at turn j', measured is closest to the passage time Toal|k of dawn i considered at turn j considered.

[0123] Advantageously, the method for measuring the deformation of the blades 18 of the turbomachine 2 continues with a step 38 of characterizing the types of response of the blades 18, in particular synchronous and asynchronous responses, and then with a step 40 of calculating the stresses during which the calculated dynamic deflections are converted into stresses.

Claims

Demands

1. A method for measuring the deformation of blades (18) of a rotor of a turbomachine (2), the turbomachine (2) comprising at least one radially internal sensor (20) configured to perform blade (18) transit time measurements from a radially internal measuring point (26), and a plurality of radially external sensors (22) configured to perform blade (18) transit time measurements from radially external measuring points (28, 30) having different azimuths, the distance between each radially external measuring point (28, 30) and an axis of rotation of the turbomachine (2) being strictly greater than the distance between said radially internal measuring point (26) and the axis of rotation of the turbomachine (2), the method comprising: - calculating, for each radially external sensor (22), for each blade (18), and for each revolution made by the rotor, the difference between, on the one hand,the passage time of the blade (18) considered, measured by the radially external sensor (22) considered at the considered revolution, and, on the other hand, the passage time of one of the blades (18) which is measured by said radially internal sensor (20) or by one of the radially internal sensors (20) and which is the passage time closest to said passage time of the blade (18) considered, measured by the radially external sensor (22) considered at the considered revolution; and - the use, in a model for each radially external sensor (22) considered, for each blade (18) considered, and for each revolution considered, of the corresponding calculated differences to deduce dynamic deflections of the blades (18).

2. A method for measuring the deformation of blades (18) of a rotor of a turbomachine (2) according to claim 1, the turbomachine (2) comprising a plurality of radially internal sensors (20) configured to perform blade (18) transit time measurements from radially internal measuring points (26) having different azimuths, wherein the method comprises: - the calculation, for each radially external sensor (22), for each blade (18), and for each revolution of the rotor, of the difference between, on the one hand, the passage time of the blade (18) considered measured by the radially external sensor (22) considered at the considered turn and, on the other hand, the passage time of one of the blades (18) which is measured by one of the radially internal sensors (20) and which is the passage time closest to said passage time of the blade (18) considered measured by the radially external sensor (22) considered at the considered turn.

3. Method for measuring the deformation of blades (18) of a rotor of a turbomachine (2) according to claim 1 or 2, comprising prior numerical simulations, in particular by finite elements, to determine an inside radial distance corresponding to a blade vibration node (18), said or each radially inside sensor (20) being located at said inside radial distance.

4. Method for measuring the deformation of blades (18) of a rotor of a turbomachine (2) according to any one of claims 1 to 3, comprising prior numerical simulations, in particular by finite elements, to determine an outer radial distance corresponding to a blade vibration antinode (18), each radially outer sensor (22) being located at said outer radial distance.

5. Method for measuring the deformation of blades (18) of a rotor of a turbomachine (2) according to any one of claims 1 to 4, comprising calculating an instantaneous regime of the turbomachine (2) as a function of the passage times of the blades (18) measured by said or the radially internal sensor(s) (20) and of angular positions of the rotor associated therewith, said modeling comprising using the calculated instantaneous regime of the turbomachine (2) to deduce the dynamic deflections of the blades (18).

6. A method for measuring the deformation of blades (18) of a rotor of a turbomachine (2) according to claim 5, wherein the calculation of the instantaneous speed of the turbomachine (2) comprises: - the formation of pairs of values, for said or each radially internal sensor (20), for each blade (18), and for each revolution made by the rotor, between, on the one hand, the passage time of the blade (18) considered measured by the radially internal sensor (20) considered at the revolution considered and, on the other hand, the associated angular position of the rotor which is measured cumulatively; and - the ranking of all pairs of values ​​in ascending order of the passage times measured by said or the radially internal sensors (20).

7. A method for measuring the deformation of blades (18) of a rotor of a turbomachine (2) according to claim 6, wherein the calculation of the instantaneous speed of the turbomachine Reg(t) is performed piecewise Regp(t), said calculation comprising, for any time t between two values ​​of passage times ToaRp, ToaRp+i measured by said or the radially internal sensors (20) which are successive in ascending order, the intermediate calculations of: ■ RptrDF - (_____) v 1 with ^p+i the values ​​of the ( ToaRp-ToaRp / A 6 angular position of the rotor, measured in degrees, associated with the measured passage times ToaRp, ToaRp+i, measured in seconds; and Mov with Ne the number of radially internal sensors (20); to determine ReS^ -ReSP May' Regp(t) ~ ToaRp+l-ToaRp ' (t~ ToaRp) + Regp

8. Method for measuring the deformation of blades (18) of a rotor of a turbomachine (2) according to any one of claims 1 to 7, wherein said modeling includes the use of a correction parameter for an azimuth offset between the radially outer sensor (22) considered and the radially inner sensor (20) which measures the passage time closest to the passage time of the blade (18) considered at the revolution considered.

9. A method for measuring the deformation of blades (18) of a rotor of a turbomachine (2) according to any one of claims 1 to 8, wherein said modeling includes the calculation of the dynamic deflections of the blades (18) as: . Re^Toa._ / \ Diyjk - 2^ ■ Radius • 60 • ( T oa^-Tref ) - Radius • t g0 (y + fi} where i is the blade (18) considered; j is the revolution considered; k is the radially external sensor (22) considered;

10. Radius is the distance between the axis of rotation of the turbomachine (2) and the radially external measuring point (28, 30) of the radially external sensor (22) considered; Reg(t) the instantaneous regime of the turbomachine (2); Toal|k is the passage time of the blade (18) considered, measured by the radially external sensor (22) considered at the considered revolution; Tref is the passage time of one of the blades (18) which is measured by said radially internal sensor (20) or by one of the radially internal sensors (20) and which is the passage time closest to said passage time of the blade (18) considered, measured by the radially external sensor (22) considered at the considered revolution; y is the oriented angle between the radially external sensor (22) considered and the radially internal sensor (20) which measures the passage time closest to the passage time of the blade (18) considered at the considered revolution; [3 is a correction parameter for an azimuth offset between the radially outer sensor (22) considered and the radially inner sensor (20) which measures the passage time closest to the passage time of the blade (18) considered at the considered turn. Turbomachine (2) comprising at least one radially internal sensor (20) configured to perform blade passage time measurements (18) from a radially internal measuring point (26), and a plurality of radially external sensors (22) configured to perform blade passage time measurements (18) from radially external measuring points (28, 30) having different azimuths, the distance between each radially external measuring point (28, 30) and an axis of rotation of the turbomachine (2) being strictly greater than the distance between said radially internal measuring point (26) and the axis of rotation of the turbomachine (2), characterized in that the turbomachine (2) comprises a computer (16) configured to implement the method for measuring the deformation of blades (18) of a rotor of a turbomachine (2) according to any one of claims 1 to 9.

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