Multiphase flow or structural corrosion / erosion imaging by acousto-electric tomography

Abstract

Multiphase flow or structural corrosion / erosion imaging by acousto-electric tomography An electronic device for generating and acquiring acousto-electric tomography signal for structural corrosion / erosion imaging and / or multiphase flow imaging uses a sensor array comprising at least one pair of sensors (140 to 14N) including a transmitter sensor (CE) and a receiver sensor (CR).The device comprises: - a signal generation module configured to generate, for each transmitting sensor (TS) of each sensor pair (140 to 14N), a two-component signal comprising both an acoustic excitation component and an electrical excitation component mixed together within said two-component signal; - a signal acquisition module configured to acquire a signal representative of the signal received by each receiving sensor (RS) of each sensor pair (140 to 14N), and, from said representative signal, to generate two distinct received components respectively dedicated to acoustic tomography and electrical impedance tomography. Figure 1.

Description

Title of the invention: Imaging of multiphase flow or corrosion / erosion of structure by acousto-electric tomography

[0001] The present invention relates to an electronic device for generating and acquiring an acousto-electric tomography signal for structural corrosion / erosion imaging and / or multiphase flow imaging by using a network of acousto-electric tomography sensors, said network comprising at least one pair of sensors, said pair comprising a transmitter sensor and a receiver sensor.

[0002] The present invention also relates to an associated system for acousto-electric tomography for structural corrosion / erosion imaging and / or multiphase flow imaging.

[0003] The present invention relates on the one hand to the field of flow measurement, the measurement of multiphase flows and on the other hand to the field of structural health monitoring or SHM (from the English Structural Health Monitoring) aimed at detecting and characterizing, in a planned manner, in real time, or even periodically (e.g. once a day in particular), damage (i.e. anomalies) of structures / infrastructures via a set of sensors integrated into each structure / infrastructure, said sensors being made to "live" with said structure / infrastructure, so that we speak of "integrated health monitoring" making it possible to monitor the state of health of the structure throughout the life of the structure, as well as that of non-destructive testing (NDT) by measurement on demand.Such structural anomalies correspond to modifications of the physical and / or geometric properties of the structure considered likely to affect its performance and / or reliability.

[0004] More specifically, the present invention relates to structural imaging, in particular thin metal structures such as plates or tubes, in order to image in particular corrosion / erosion or loss of thickness in pipes, and / or multiphase fluid imaging in order to image in particular in real time the void ratio in a flow mixing water and air.

[0005] Currently two distinct techniques are used for imaging multiphase structures or fluids, namely on the one hand electrical impedance tomography (EIT) by electromagnetic waves, an example of which is described by L. Borcea in the article entitled: "Electrical impedance tomography" OP Publishing, Inverse Problems, vol. 18, n° %16, p. R99, 2002 and on the other hand acoustic tomography by mechanical waves such as:

[0006] - volume wave acoustic tomography, an example of which is described by M. Rahimana et al. in the article entitled: "An investigation on Chemical bubble column using ultrasonic tomography for imaging ofgas profiles" Sensors and Actuators B: Chemical, vol. 202, pp. 46-52, 2014, or

[0007] - acoustic tomography by guided elastic waves, an example of which is described by T. Druet et al. in the article entitled: “Autocalibration method for guided wave tomography with undersampled data” Wave Motion, pp. 265-283, 2019, the waves used being waves guided by the wall of the structure studied in particular for corrosion imaging of the structure.

[0008] Electrical impedance tomography (EIT) is a non-invasive, non-destructive technique that allows the interior of an object (i.e., structure) to be viewed in real time and continuously by measuring the electrical properties, in particular the potential and the electric current, of this object at its surface. This robust approach is particularly suitable for carrying out non-intrusive measurements in industrial environments, for example under high pressures and / or high temperatures. In other words, the electrical tomography measurement uses Ohm's law to reconstruct the electrical conductivity map from the information in potentials and electric currents on the periphery. The electrical potentials are imposed on the electrodes placed around and in contact with the study area.

[0009] Electrical impedance tomography (EIT) consists more precisely of injecting electrical currents or potentials by means of a set of non-intrusive electrodes arranged on the surface of the object being monitored and then measuring the electrical potentials or currents on the surface of this object (i.e. structure).

[0010] The electrodes are suitable for being in contact only with the outer surface of the object. However, in the case where the surface of the object is made of metal, the electrodes are suitable for passing through the wall and being in contact with the fluid.

[0011] The impedance map inside the object is reconstructed by solving the associated inverse problem.

[0012] It is known to implement multiplexing in which an excitation signal is imposed on a group of electrodes. The different groups of electrodes are selected in real time by means of multiplexers or electronic switches or, in frequency in the Fourier space. The set of excitation series (voltage or current) and measurements (current or voltage respectively) make it possible to obtain a data matrix containing the values ​​of the measurements for each electrode according to each excitation pattern. These matrices are used to reconstruct an electrical impedance tomography (EIT) image.

[0013] An electrical impedance tomography (EIT) image thus comprises the measurement data of all the groups of excited electrodes suitable for use in determining the potential distribution and solving the inverse problem of reconstruct the distribution of material properties within the object, such as electrical conductivity, permittivity, etc.

[0014] Acoustic tomography by mechanical waves corresponding to volume waves (for example longitudinal pressure waves in water) or guided elastic waves (for example Lamb waves in plates), is based on the same principle, whatever the technical problem to be solved relating to multiphase flow or corrosion / erosion imaging, namely the use of a network of sensors, for example piezoelectric transducers, such a network being capable of emitting and receiving mechanical waves in a medium to probe it. Mechanical wave tomography also includes the acquisition of waves for all the pairs of sensors in the distribution (i.e. the network of sensors used) and their transformation into the form of digitized signals. The digitized signals are then the input data of a method capable of solving an inverse problem making it possible to image the medium.Thus, mechanical wave tomography makes it possible to quantify, for example, the positions and extent of bubbles in a flow or the loss of thickness of a structure due to corrosion or erosion.

[0015] It should be noted that the main characteristic differentiating guided elastic waves used to measure corrosion / erosion or loss of structural thickness from bulk waves used to measure multiphase flow is that guided elastic waves are dispersive while bulk waves are not. This dispersion property is used to quantitatively trace the thickness in the case of corrosion imaging, thanks to what are called dispersion curves which link the properties of the waves such as their phase or group velocities or even the wavelength or wave number as a function of the frequency and thickness of the structure.

[0016] In acoustic tomography, in order to solve the inverse problem of reconstructing an image from signals, there are different acoustic tomography techniques which are more or less suitable depending on what one is trying to image, namely:

[0017] - diffraction tomography using a wave approach, suitable for an ap application to:

[0018] - flow imaging in particular to detect a small bubble size in front of the wavelength used, because associated with a predominant diffraction phenomenon,

[0019] - corrosion imaging to detect small structural defects,

[0020] - time-of-flight or attenuation tomography using a ray approach, suitable for application to:

[0021] - flow imaging in particular to detect a large bubble size in front of the wavelength used, because associated with a phenomenon of reflection on the bubbles predominant and attenuation on direct transmission paths,

[0022] - corrosion imaging to detect large structural defects,

[0023] - amplitude tomography for all possible paths for a pair of given transmitter and receiver sensors, in particular the transmitter paths to the mapping point, then to the receiver, according to a principle substantially close to the principle of the TFM method (from the English Total Focusing Method), adapted to an application to flow imaging in particular to detect a large bubble size compared to the wavelength used, because associated with a predominant phenomenon of reflection on the bubbles. The contours of the bubbles are reconstructed for this type of acoustic tomography by amplitude tomography.

[0024] It should further be noted that existing techniques make it possible to couple several of the aforementioned types of acoustic tomography in order to take advantage of the benefits of the different acoustic tomography methods.

[0025] Electrical impedance tomography by electromagnetic waves, and acoustic tomography by guided volume or elastic mechanical waves, respectively have advantages and disadvantages for imaging a multiphase medium or for imaging corrosion / erosion or loss of thickness in pipes.

[0026] Indeed, to image a multiphase medium, for example an air / water flow, the two aforementioned tomography techniques used independently are not completely satisfactory, because on the one hand electrical impedance tomography provides:

[0027] - poor visualization of the vacuum rate when there is little air, in particular a proportion less than 10%;

[0028] - good resolution at the edge (i.e. near the sensors) but an image degraded in the center;

[0029] - very fast measurements at low frequency, fast but not very precise at high frequency ;

[0030] and on the other hand acoustic tomography, by volume waves, provides, in a complementary manner:

[0031] - poor visualization of the vacuum rate when there is a lot of air in particular a proportion greater than 10%, because Fonde does not (or hardly) pass into transmission;

[0032] - good resolution in the center but a degraded image at the edge (i.e. near sensors);

[0033] - slow measurements at low frequency, and very precise and relatively fast at high frequencies.

[0034] And with regard to corrosion / erosion imaging, on the one hand electrical impedance tomography provides:

[0035] - good resolution at the edge (i.e. near the sensors) but an image degraded in the center;

[0036] - the possibility of imaging large areas of the order of several meters;

[0037] - non-quantitative imaging;

[0038] and on the other hand acoustic tomography, by guided elastic waves, provides, in a complementary manner:

[0039] - good resolution in the center and a degraded image at the edge (i.e. near the sensors);

[0040] - the possibility of imaging medium-sized areas, of the order of a meter, up to a few meters maximum;

[0041] - quantitative imaging.

[0042] In other words, currently large void ratios (e.g., greater than 10%) are imaged by electrical impedance tomography, which works very well when there is a lot of gas. On the other hand, electrical impedance tomography begins to give poor results for a void ratio below 1% (e.g., void ratio 102, which corresponds, for example, to the imaging of a single bubble with a diameter of two to three centimeters for a DN300 type tube). Low void ratios (e.g., up to 105, which corresponds, for example, to the imaging of a single bubble with a diameter of 1 mm for a DN300 tube) are imaged by acoustic tomography, which works very well only if there are few bubbles and they are small.

[0043] In terms of sensitivity zone, it is known that electrical impedance tomography images rather well at the edge of the domain and that acoustic tomography images rather well in the center of the domain.

[0044] Finally, in terms of scanning speed, electrical impedance tomography allows rapid acquisitions of large inclusions which, in acoustic tomography, may on the contrary require scanning with low frequencies and therefore a significant acquisition time.

[0045] Thus, currently, in the field of imaging corrosion / erosion or loss of thickness of structure(s) and / or imaging of multiphase fluid in order to image in particular in real time the void ratio in a flow mixing water and air, there is no solution making it possible to effectively couple acoustic tomography and electrical impedance tomography, which implies making their respective associated images perfectly superimposable in the context of flows.

[0046] The aim of this invention is therefore to propose a solution making it possible, at least partially, to achieve such a coupling, currently non-existent, of acoustic tomography with electrical impedance tomography to provide a tomography subsequently called acousto-electric (or conversely electro-acoustic) tomography applicable to the imaging of corrosion / erosion or losses of structure thickness(es) and / or multiphase fluid imaging.

[0047] To this end, the invention relates to an electronic device for generating and acquiring an acousto-electric tomography signal for structural corrosion / erosion imaging and / or multiphase flow imaging by using a network of acousto-electric tomography sensors, said network comprising at least one pair of sensors, said pair comprising a transmitter sensor and a receiver sensor, said device comprising:

[0048] - a signal generation module configured to generate, for each sensor transmitter of each pair of sensors of said network, a two-component signal, said two-component signal comprising both an acoustic excitation component and an electrical excitation component mixed together within said two-component signal,

[0049] - a signal acquisition module configured to:

[0050] - acquire a signal representative of the signal received by each receiver sensor of each couple, and

[0051] - from said representative signal, to generate two distinct received components respectively dedicated to acoustic tomography and electrical impedance tomography.

[0052] Such an electronic device for generating and acquiring an acousto-electric tomography signal makes it possible to simultaneously perform excitations and / or acquisition of acoustic and electrical measurements which make it possible to simultaneously obtain two distinct received components respectively dedicated to acoustic tomography and electrical impedance tomography and combined within the same generated and / or acquired signal.

[0053] In other words, the electronic device for generating and acquiring an acousto-electric tomography signal according to the present invention is common to acoustic tomography and electrical impedance tomography, which makes it possible to avoid duplication of a digital system, namely a system dedicated to acoustic tomography and one dedicated to electrical impedance tomography, to generate via a single output channel a signal coupling two excitations dedicated respectively to acoustic tomography and electrical impedance tomography, and to acquire and process a single measurement signal representative of the signal received by each receiver sensor of each pair of a network of acousto-electric tomography sensors, this measurement signal also coupling, due to the two-component excitation, two measurement components dedicated respectively to acoustic tomography and electrical impedance tomography.

[0054] In addition, the electronic device for generating and acquiring acousto-electric tomography signals according to the present invention allows, in terms of signal processing, to advantageously couple the components associated respectively with acoustic tomography and electrical impedance tomography, which allows simultaneous excitation and measurement in time of the signals associated with each of these tomography techniques, and consequently contributes to obtaining images associated respectively with these two techniques which are perfectly superimposable in the context of flows.

[0055] In other words, the electronic device for generating and acquiring acousto-electric tomography signals according to the present invention provides a technical solution for implementing these simultaneous excitations and measurements.

[0056] Acoustic tomography and electrical impedance tomography being complementary as seen previously, their simultaneous deployment mutually compensates for the shortcomings of their separate use.

[0057] According to other advantageous aspects of the invention, the electronic device for generating and acquiring an acousto-electric tomography signal according to the present invention comprises one or more of the following characteristics, taken in isolation or in all technically possible combinations:

[0058] - the same sensor being suitable for being a transmitter for at least one pair then receiver for at least one other couple,

[0059] - said electrical excitation component is a component whose voltage is in lower than a first predetermined voltage threshold, and said acoustic excitation component is a component whose voltage is higher than a second predetermined voltage threshold, said second voltage threshold being higher than or equal to said first voltage threshold;

[0060] - said first voltage threshold is substantially equal to one volt while said second voltage threshold is substantially equal to one hundred volts;

[0061] - said electrical excitation component corresponds to a mono component chromatic, and wherein said acoustic excitation component is a broadband component;

[0062] - said electrical excitation component is a component whose frequency is less than a first predetermined frequency threshold, and wherein said acoustic excitation component is a component whose frequency is greater than a second predetermined frequency threshold, said second frequency threshold being greater than or equal to said first frequency threshold;

[0063] - for multiphase flow imaging, said first frequency threshold is substantially equal to 100 kHz while said second frequency threshold is substantially equal to 150 kHz;

[0064] - for structural corrosion / erosion imaging, said first threshold of frequency is substantially equal to 10 kHz while said second frequency threshold is substantially equal to 20 kHz;

[0065] - said generation module comprises a mixer having as inputs said acoustic excitation component and said electrical excitation component and for outputting said two-component signal, said mixer corresponding to an adder;

[0066] - said generation module further comprises a set of electronic switches electronics configured to multiplex in time division the acoustic excitation components and / or the electrical excitation components of a plurality of two-component signals, each two-component signal of said plurality being associated with a separate transmitter sensor;

[0067] - said generation module further comprises a frequency multiplexing tool configured to multiplex in frequency division the acoustic excitation components and / or the electrical excitation components of a plurality of two-component signals, each two-component signal of said plurality being associated with a separate emitting sensor;

[0068] - the acquisition module comprises:

[0069] - a predetermined set of band-pass filters, said set of band-pass filters band being configured to discriminate, within the signal representative of the signal received by each receiving sensor of each pair, the received component dedicated to acoustic tomography from the received component dedicated to electrical impedance tomography; or

[0070] - a high-pass filter to recover the received component dedicated to tomography acoustic, and a low-pass filter to recover the received component dedicated to electrical impedance tomography.

[0071] - the acquisition module is capable of applying a predetermined set of Fourier transforms, said set of Fourier transforms being configured to discriminate, within the signal representative of the signal received by each receiving sensor of each pair, the received component dedicated to acoustic tomography from the received component dedicated to electrical impedance tomography.

[0072] The invention also relates to an acousto-electric tomography system for imaging structural corrosion / erosion and / or multi-phase flow imaging, the system comprising:

[0073] - an acousto-electric tomography sensor network comprising at least one pair of sensors, said pair comprising a transmitter sensor and a receiver sensor

[0074] - at least one electronic device for generating and acquiring a signal of to acoustoelectric mography as defined above,

[0075] - a tomographic imaging device;

[0076] the electronic signal generation and acquisition device being suitable for:

[0077] - excite each emitting sensor of each pair of sensors of said network in using said two-component signal,

[0078] - providing as input to said tomographic imaging device two sets of separate data respectively obtained from the two separate received components respectively dedicated to acoustic tomography and electrical impedance tomography.

[0079] According to other advantageous aspects of the invention, the acousto-electric tomography system for imaging corrosion / erosion of structure and / or multiphase flow imaging comprises one or more of the following characteristics, taken individually or in all technically possible combinations:

[0080] - the same sensor being suitable for being a transmitter for at least one pair then receiver for at least one other couple;

[0081] - said tomography device is capable of independently generating:

[0082] - an acoustic tomography image from the received component dedicated to the acoustic tomography;

[0083] - an electrical impedance tomography image from the received component dedicated to electrical impedance tomography;

[0084] and recombining said acoustic tomography image with said electrical impedance tomography image to form an acoustoelectric tomography image,

[0085] - said tomography device is capable of directly generating an image of to acousto-electric mography by processing together the received component dedicated to acoustic tomography and the received component dedicated to electrical impedance tomography, via a predetermined iterative inversion tool, or via a predetermined artificial intelligence tool;

[0086] - each acousto-electric tomography sensor of said network comprises two separate excitation and measurement elements, co-located within said sensor, dedicated respectively to tomographic measurement by electrical impedance and to acoustic tomographic measurement, and capable of being excited simultaneously via two distinct components of a two-component signal, the excitation and measurement element dedicated to tomographic measurement by electrical impedance being capable of being excited by the electrical excitation component of said two-component signal, and the excitation and measurement element dedicated to acoustic tomographic measurement being capable of being excited at least by the acoustic excitation component of said two-component signal.

[0087] These characteristics and advantages of the invention will appear more clearly on reading the description which follows, given solely by way of non-limiting example, and made with reference to the appended drawings, in which:

[0088] - [Fig.l] [Fig.l] is a diagram illustrating an acousto-tomography system electrical corrosion / erosion imaging of structure and / or multiphase flow imaging according to the present invention;

[0089] - [Fig.2] [Fig.3] [Fig.4] [Fig.5] Figures 2 to 5 are diagrams illustrating dif various variants of the electronic device for generating and acquiring a signal capable of exciting an acousto-electric tomography sensor according to the present invention;

[0090] - [Fig.6] [Fig.6] illustrates three examples of arrangement of a tomography sensor acousto-electric according to the present invention;

[0091] - [Fig.7] [Fig.7] illustrates in time and frequency the acousto-electric signal suitable for being generated according to the present invention.

[0092] In the remainder of the description, the expression “substantially equal to” is understood as a relationship of equality to plus or minus 10%, that is to say with a variation of at most 10%, more preferably as a relationship of equality to plus or minus 5%, that is to say with a variation of at most 5%.

[0093] [Fig.l] is a representation of an acousto-electric tomography system 10 for structural corrosion / erosion imaging and / or multiphase flow imaging according to the present invention.

[0094] More precisely, such a system 10 firstly comprises a network 12 of acousto-electric tomography sensors comprising at least one pair of sensors, said pair comprising a transmitter sensor and a receiver sensor. It should be noted that for two different pairs of sensors (i.e. different by at least one of the sensors of said pair) the same sensor is capable of being a transmitter for at least one pair then a receiver for at least one other pair (distinct from the pair(s) for which it is a transmitter).

[0095] In [Fig.l], the network comprises in particular N+1 pairs 14, namely pairs 140 to 14n as represented and each pair comprises a transmitter sensor CE and a receiver sensor CR. More precisely, each sensor (transmitter CE or receiver CR) of acousto-electric tomography of said network 12 comprises two distinct excitation and measurement elements, co-located within said sensor, dedicated respectively to the tomographic measurement by electrical impedance and to the acoustic tomographic measurement, and capable of being excited simultaneously via two distinct components of a two-component signal, the excitation and measurement element dedicated to the tomographic measurement by electrical impedance being capable of being excited by the electrical excitation component of said two-component signal, and the excitation and measurement element dedicated to the acoustic tomographic measurement being capable of being excited at least by the acoustic excitation component of said two-component signal..

[0096] The structure and peculiarities of acoustoelectric tomography sensors will be detailed below in relation to figures 2 to 6.

[0097] The system according to the present invention further comprises at least one electronic device 16 for generating and acquiring an acousto-electric tomography signal.

[0098] More precisely, said electronic device 16 for generating and acquiring an acousto-electric tomography signal firstly comprises a signal generation module G configured to generate, for each transmitter sensor CE of each pair 140 to 14n of sensors of said network 12, a two-component signal, said two-component signal comprising both an acoustic excitation component and an electrical excitation component mixed together within said two-component signal, such a signal being described in detail and illustrated subsequently by [Fig.7].

[0099] Furthermore, said electronic device 16 for generating and acquiring an acousto-electric tomography signal comprises a signal acquisition module A configured to acquire a signal representative of the signal received by each receiving sensor of each pair, and from said representative signal, to generate two distinct received components respectively dedicated to acoustic tomography and electrical impedance tomography.

[0100] Thus, the electronic device 16 for generating and acquiring a signal according to the present invention is capable of:

[0101] - excite each CE transmitter sensor of each pair 140 to 14N of sensors of said network 12 using said two-component signal,

[0102] - provide as input to a tomographic imaging device 18 two sets of separate data respectively obtained from the two separate received components respectively dedicated to acoustic tomography and electrical impedance tomography.

[0103] In other words, the electronic signal generation and acquisition device 16 according to the present invention is capable of acquiring the signals for the pairs 140 to 14N of transmitter / receiver sensors for the entire distribution of sensors, signals subsequently digitized as input data for an inversion algorithm making it possible to calculate an image of the structure inspected by acousto-electric tomography.

[0104] In addition, the acousto-electric tomography system 10 further comprises said tomographic imaging device 18.

[0105] According to a first variant embodiment, not shown, said tomography device 18 is capable of independently generating:

[0106] - an acoustic tomography image from the received component dedicated to the acoustic tomography;

[0107] - an electrical impedance tomography image from the received component dedicated to electrical impedance tomography;

[0108] and recombining said acoustic tomography image with said electrical impedance tomography image to form an acoustoelectric tomography image, in order to take advantage of the advantages of electrical impedance tomography and the advantages of acoustic tomography.

[0109] According to a second variant embodiment, not shown, said tomography device 18 is capable of directly generating an acousto-electric tomography image by processing together the received component dedicated to acoustic tomography and the received component dedicated to electrical impedance tomography, via a predetermined iterative inversion tool, or via a predetermined artificial intelligence tool.

[0110] Indeed, as indicated previously, within the acquisition module A of the generation and acquisition device 16, the matrix of measured signals is digitally filtered to separate the electrical impedance tomography data from the acoustic tomography data, and provide this data to the tomography device 18. The images are then either, according to said first variant mentioned above, calculated by the tomography device 18 independently and then finally intelligently recombined according to the intended application and according to the complementarities, or, according to said second variant mentioned above, calculated together via predetermined iterative inversion or artificial intelligence algorithms.

[0111] According to an optional variant, it is also possible to reconstruct images from the raw data associated respectively with acoustic tomography and electrical impedance tomography by image reconstruction using deep learning.

[0112] Furthermore, the reconstruction of the images from the acousto-electric data involves images that are perfectly superimposable in the context of flows. This superposition in time and space is obtained by combining the elements 12, 16 and 18 to have identical boundary conditions and to reconstruct superimposable images of electrical impedance tomography on the one hand and acoustic tomography on the other hand, suitable for being perfectly superimposed by said tomography device 18 according to one of the two preceding variants.

[0113] Such a system 10 provides an efficient coupling of the two methods of electrical impedance tomography and acoustic tomography because it provides simultaneity of measurement in time, via the electronic device 16 for generating and acquiring the signal, and in space, via the acousto-electric tomography sensors. Such simultaneity in time and space makes it possible to obtain an exploitable coupling of the two imagings associated respectively with electrical impedance tomography and acoustic tomography, the acoustic tomography being able to be a diffraction tomography, a time-of-flight tomography, a path attenuation tomography direct, amplitude tomography by reflection on the edges of the bubbles, a combination of these different types of acoustic tomography.

[0114] Subsequently, each of the elements 12, 14, 16 and 18 constituting this system 10 will be described according to embodiments specific to each element, which can be used independently or advantageously combined within said system 10.

[0115] Subsequently, optional additions, not shown, to the electronic signal generation and acquisition device 16 are described firstly because they are suitable for generating, firstly, an excitation of the CE transmitter sensor adapted to the effective coupling of acoustic tomography and electrical impedance tomography in the specific fields of, on the one hand, flow measurement, multiphase flow measurement and, on the other hand, structural health monitoring or SHM (from the English Structural Health Monitoring) aimed at detecting and characterizing, in a planned or periodic manner, damage (i.e. anomalies) of structures / infrastructures, as well as that of non-destructive testing (NDT) by on-demand measurement.

[0116] According to a first optional addition relating to the electronic signal generation and acquisition device 16, said electrical excitation component is a component whose voltage is lower than a first predetermined voltage threshold, and said acoustic excitation component is a component whose voltage is higher than a second predetermined voltage threshold, said second voltage threshold being higher than or equal to said first voltage threshold.

[0117] According to a variant of this addition, said first voltage threshold, associated with the electrical excitation component, is substantially equal to one volt while said second voltage threshold, associated with the acoustic excitation component, is substantially equal to one hundred volts.

[0118] As an optional addition, said electrical excitation component corresponds to a monochromatic component, and in said acoustic excitation component is a broadband component (i.e. substantially resembling a wave packet), corresponding for example to a broadband signal comprising n sinusoid cycles windowed by a Hann window as described below, or by other types of windows such as a Blackman-Harris window, a rectangular window, a triangular window, etc., or to a square wave or burst signal. In other words, by "broadband", it is meant that the bandwidth of said acoustic excitation component corresponds to the spectral band of the wave packet chosen for the acoustic component. Given that the number of cycles of the emitted packet is generally low, the spectral band is consequently wide.

[0119] As an optional addition, said electrical excitation component is a component whose frequency is lower than a first predetermined frequency threshold, and wherein said acoustic excitation component is a component whose frequency is higher than a second predetermined frequency threshold, said second frequency threshold being higher than or equal to said first frequency threshold.

[0120] According to this optional addition, the electrical excitation component whose frequency is lower than the first predetermined frequency threshold is qualified as a low frequency (LF) component, while said acoustic excitation component whose frequency is higher than a second predetermined frequency threshold is qualified as a high frequency (HF) component.

[0121] In particular, for multiphase flow imaging, said first frequency threshold is substantially equal to 100 kHz while said second frequency threshold is for example substantially equal to 150 kHz, or even 300 kHz. According to another example for this multiphase flow imaging application, said first threshold is equal to said second threshold and are substantially equal to 100 kHz, the electrical excitation component having a frequency strictly lower than this common threshold, and the acoustic excitation component having a frequency strictly higher than this common frequency threshold.

[0122] On the other hand, for structural corrosion / erosion imaging, said second frequency threshold is for example greater than 20kHz, or between 50 kHz and 200 kHz, while said first threshold is for example substantially equal to 10kHz. According to another example for this structural corrosion / erosion imaging application, said first threshold is equal to said second threshold and are substantially equal to 15kHz, the electrical excitation component having a frequency strictly lower than this common threshold, and the acoustic excitation component having a frequency strictly higher than this common frequency threshold.

[0123] The choice of said first and second voltage thresholds and / or said first and second frequency thresholds above makes it possible to obtain transmission and reception of waves at voltages and frequencies intelligently chosen to allow simultaneous measurement.

[0124] As an optional addition, said generation module G comprises a mixer having as inputs said acoustic excitation component and said electrical excitation component and as output said two-component signal, said mixer corresponding, for example, to an adder.

[0125] As an optional addition, said generation module G further comprises a set of electronic switches configured to time-division multiplex the acoustic excitation components and / or the electrical excitation components of a plurality of two-component signals, each two-component signal of said plurality being associated with a separate transmitter sensor.

[0126] Such time division multiplexing, using electronic switches, makes it possible to distribute the signals temporally over the set of excitation and measurement elements dedicated to the tomographic measurement by electrical impedance of the network 12 and over the set of excitation and measurement elements dedicated to the acoustic tomographic measurement.

[0127] As an optional addition, said generation module G further comprises a frequency multiplexing tool configured to multiplex in frequency division the acoustic excitation components and / or the electrical excitation components of a plurality of two-component signals, each two-component signal of said plurality being associated with a separate emitting sensor.

[0128] For example, according to this optional supplement, such frequency division multiplexing is obtained by applying the “ONE-SHOT” technique (from the English ONe Excitation for Simultaneous High-speed Operation Tomography) described by M. Damajou et al. in the article entitled “High Speed ​​E1T With Multifrequency Excitation Using EPGA and Response Analysis Using EDM” from 2020, or the “COLTRANE” technique (from the English Continuous Overlapping operations with Linear Trigonometry Response ANalysis for EIT) described in the document WO 2022 200558 Al or in the thesis of M. Damajou, entitled “A Novel approach to High-Speed ​​Electrical Impedance Tomography with Frequency Division Multiplexing” from October 2020. Such frequency division multiplexing makes it possible in particular to add simultaneity in the two techniques of acoustic and electrical impedance tomography.

[0129] Such optional frequency division multiplexing can, as required, be combined with the aforementioned optional time division multiplexing.

[0130] As an optional addition, said acquisition module A comprises in an analog manner:

[0131] - a predetermined set of band-pass filters, said set of band-pass filters band being configured to discriminate, within the signal representative of the signal received by each receiving sensor of each pair, the received component dedicated to acoustic tomography from the received component dedicated to electrical impedance tomography, or

[0132] - a high-pass filter to recover the received component dedicated to tomography acoustic, and a low-pass filter to recover the received component dedicated to electrical impedance tomography.

[0133] For example, two band-pass filters are used to filter respectively on the one hand the low-frequency band BF associated with the received component dedicated to electrical impedance tomography, and the high-frequency band HF associated with the received component dedicated to acoustic tomography.

[0134] The predetermined set of bandpass filters has the advantage, compared to the aforementioned combination of a high-pass filter dedicated to acoustic tomography and a low-pass filter dedicated to electrical impedance tomography, of filtering at least all the noise outside the frequency band of interest by adjusting the cut-off frequencies as close as possible to the working frequencies specific to each application, for example by using a first bandpass filter corresponding to the frequency interval from 90 to 210 kHz to filter an acoustic component at 150 kHz and by using a second bandpass filter corresponding to the frequency interval from 5 to 15 kHz to filter an electrical component at 10 kHz.

[0135] As an alternative to this analog complement, or as a digital complement to this analog complement, the acquisition module is capable of applying a predetermined set of Fourier transforms, said set of Fourier transforms being configured to discriminate, within the signal representative of the signal received by each receiver sensor of each pair, the received component dedicated to acoustic tomography from the received component dedicated to electrical impedance tomography.

[0136] More precisely, fast Fourier transforms are defined such that the frequency of their iteration is an integer divisor of the frequencies of the generated analog electrical signals, under the Nyquist limit.

[0137] In view of the above, the electronic signal generation and acquisition device 16 according to the present invention is therefore configured to provide simultaneity in time of the processing of the emitted and measured signals.

[0138] In order to ensure simultaneity in time, it is important that the emission and the measurement are simultaneous and to do this, according to the present invention, at the emission to excite each emitting sensor CEj distinctly or not, from one pair of sensors 14 to another, a single signal is advantageously emitted.In other words, if we consider N+1 pairs of sensors distinct from one pair to another by one of the transmitter or receiver sensors composing each pair, the two-component signal is emitted with the transmitter sensor CE0 of the first pair of index 0, and we measure preferentially simultaneously (or pair after pair which requires more time) with all the N+1 receiver sensors CR, then we emit the two-component signal with the transmitter sensor CEi of the second pair of index 1, and we measure preferentially simultaneously (or pair after pair which requires more time) with all the N+1 receiver sensors CR, and this in a repeated manner, up to the transmitter sensor CEN of the last pair of index N and therefore until we have the measurement for all the N+1 pairs of sensors.

[0139] As re-detailed later in relation to [Fig.7], the acousto-electric signal, generated by the electronic signal generation and acquisition device 16 according to the present invention, corresponds for example to the summation of the signal component necessary to carry out electrical impedance tomography and the signal component necessary to carry out acoustic tomography.

[0140] Indeed, as indicated previously, for electrical impedance tomography, the signal component of the two-component signal is a signal, for example monochromatic, of low voltage and fairly low frequency, typically of voltage less than one volt and of frequency less than 100 kHz, whereas for acoustic tomography, the signal component of the two-component signal is broadband, for example a square wave or burst signal (from the English bursf), or according to another example, a broadband signal comprising n sinusoid cycles windowed by a Hann window, high voltage and high frequency, typically of voltage greater than one hundred volts and of frequency greater than 300 kHz, such a frequency corresponding to a wavelength X less than 5 mm in water making it possible to image small bubbles.

[0141] The signal components of the two-component acousto-electric emission signal are thus the sum of two distinct bandwidths for the electrical and acoustic excitations.

[0142] Such a type of two-component signal adapted to the coupling of electrical impedance tomography and acoustic tomography also conditions, upon its emission, the simultaneous acquisition of the signal representative of the signal received by each receiver sensor coupled to a transmitter sensor of the network 12 having emitted such a signal.

[0143] In other words, the acquisition of the measurement signals for the pairs 140 to 14N of transmitter / receiver sensors for the entire distribution of sensors of the network 12 is also simultaneous to again ensure simultaneity in time allowing the acoustic tomography and the electrical impedance tomography to be coupled effectively.

[0144] Indeed, the two-component signal, generated specifically by the electronic generation and acquisition device 16, does not pose a problem of interference between the electrical measurement and the acoustic measurement for the following reasons, namely that on the one hand the fact of emitting the electrical excitation component with a low voltage will generate a mechanical wave in the medium of very low amplitude which will therefore attenuate very quickly during propagation. This acoustic wave, associated with the electrical excitation component, will therefore not be measured at the receivers and this will therefore not pollute the acoustic measurement. Only the high-frequency and high-intensity wave will be measured. As regards the electrical measurement, it is not polluted either by the high-energy and high-frequency emission of the acoustic excitation component because a simple filtering of the high frequencies allows only the monochromatic components needed to perform electrical impedance tomography to be recovered.

[0145] The discrimination of acoustic and electrical signals is therefore carried out, as indicated previously, either via bandpass filters in analog electronics, or by Fourier transforms in digital electronics.

[0146] According to the embodiment of [Fig. 1], an electronic generation and acquisition device 16 is used to generate and acquire the N+1 signals transmitted to / received from the network 12.

[0147] According to another embodiment, an electronic generation and acquisition device 16 is used per pair of transmitter sensor CE and receiver CR, or even per sensor. In other words, there are as many electronic generation and acquisition devices 16 as there are pairs of sensors or even sensors as such.

[0148] In relation to figures 2 to 5, an acousto-electric tomography sensor is shown according to different variants.

[0149] As will be seen subsequently, and as indicated previously, for all the variants illustrated by FIGS. 2 to 5, the acousto-electric tomography sensor for structural corrosion / erosion imaging and / or multi-phase flow imaging, advantageously comprises two distinct excitation and measurement elements, co-located within said sensor, dedicated respectively to the tomographic measurement by electrical impedance and to the acoustic tomographic measurement, and capable of being excited simultaneously via two distinct components of a two-component signal, and advantageously of the aforementioned two-component signal generated by the electronic generation and acquisition device 16, the excitation and measurement element dedicated to the tomographic measurement by electrical impedance being capable of being excited by an electrical excitation component of said two-component signal,and the excitation and measurement element dedicated to the acoustic tomographic measurement being capable of being excited at least by one acoustic excitation component of said two-component signal.

[0150] Such a sensor thus makes it possible to carry out simultaneous measurements in time and space of acousto-electric tomography. More precisely, such a sensor makes it possible to carry out acoustic and electrical excitations and measurements simultaneously.

[0151] Acoustic tomography and electrical impedance tomography being complementary as seen previously, their simultaneous deployment, via such a sensor, mutually compensates for the shortcomings of their separate use.

[0152] As an optional addition, said sensor is capable of operating according to three distinct operating modes comprising, a transmission mode (it is then a transmitter sensor CE), a reception mode (it is then a receiver sensor CR), and a final simultaneous transmission and reception mode, this last mode making it possible to disrupt the func operation of neighboring sensors as well as monitoring the system in order to deduce information to generate a result.

[0153] In other words, according to the present invention, exactly the same sensors are used for transmission, as for reception, for the two tomography techniques, namely electrical impedance tomography and acoustic tomography. In other words, for transmission it is not necessary to use two separate sensors for each of these tomography techniques, and likewise for reception it is not necessary to use two separate sensors for each of these tomography techniques.

[0154] Thus, in order to ensure simultaneity in space, as indicated previously, it is the same sensors which make the acquisitions for the two imaging methods, namely electrical impedance tomography and acoustic tomography.

[0155] As an optional addition, said excitation and measurement element dedicated to tomographic measurement by electrical impedance is a resistive electrode, and in which said excitation and measurement element dedicated to acoustic tomographic measurement corresponds to a piezoelectric transducer.

[0156] In emission, the piezoelectric transducer, in particular of the PZT type (based on Lead, Zirconium and Titanium or Lead Titano-Zirconate), transforms a voltage signal into mechanical deformation generating a wave in the structure, while the resistive electrode transmits an electric wave directly into the structure.

[0157] On reception, the piezoelectric transducer, in particular of the PZT type, transforms a mechanical deformation of the structure into a voltage signal which goes back to the acquisition card, while the resistive electrode measures an electric current present in the structure.

[0158] The present invention therefore proposes that the sensors with piezoelectric transducers additionally comprise at least one resistive electrode dedicated to electrical impedance tomography.

[0159] According to an optional aspect, such a piezoelectric transducer sensor, additionally comprising at least one resistive electrode dedicated to electrical impedance tomography, is capable of operating in transmission mode for at least one given pair of sensors, and in reception mode for at least one other pair (distinct from the pair(s) for which it is a transmitter), and in this case such a sensor is capable of using a dedicated signal to prevent a high transmission voltage (of the order of 100V) from rising on the acquisition channel, the measurement voltages being low (rather between the millivolt and the volt at the terminals of the piezoelectric transducer sensor, in particular of the PZT type).

[0160] In other words, we do not want the emission voltage to rise on the acquisition voices so as not to damage the electronic measurement components which are sized to receive low voltages. It is therefore necessary, when the piezoelectric transducer sensors, in particular of the PZT type, are physically used as transmitter and receiver, to open, via said dedicated signal, a switch (not shown) on the acquisition channel (reception side) corresponding to the transmission channel, precisely to prevent the high voltage from rising on the acquisition channel. For example, this can be managed by a relay (multitude of switches controlled by said dedicated signal), said dedicated signal then being a control signal for the switches.

[0161] A possible alternative solution is to use one sensor for transmission and another for reception, which makes it possible to separate the transmission circuit from the reception circuit at the cost of an increase in the number of sensors and complexity associated with increased intrusiveness in the structure.

[0162] [Fig.2] represents a first embodiment of the acousto-electric tomography sensor of the aforementioned type, specifically for an application to the imaging of a two-phase water / air flow in the nuclear field with intelligent instrumentation of a flange.

[0163] [Fig.2] represents a measuring assembly 20, according to a first variant, composed of several sensors with dual excitation systems: acoustic and electrical.

[0164] More precisely, according to the variant of [Fig.2], the acousto-electric tomography sensor schematically comprises a digital stage 22 and an analog stage 24 for signal processing.

[0165] The digital stage 22 comprises a transmission part 26 suitable for receiving, or where appropriate digitally generating, said aforementioned two-component signal and for transforming it via a digital-to-analog converter into a two-component analog excitation signal of said two excitation and measurement elements of the sensor described below.

[0166] In other words, according to a first variant this digital transmission part 26 is a digital core capable of communicating with the rest of the system 10 of [Fig.l] in particular with the aforementioned electronic generation and acquisition device 16.

[0167] According to a second variant, this digital emission part 26 is capable of generating said two-component signal itself. In other words, according to this second variant, the acousto-electric sensors of the network 12 themselves incorporate electronics comprising a digital part and an analog part capable of intrinsically providing said simultaneity in time, namely for electrical impedance tomography and for acoustic tomography.

[0168] According to this second variant, from mathematical formulas or a predetermined sequence, a two-component signal of the aforementioned type (in relation to the device generation and acquisition 16) is then generated via two separate digital component generators 28 and 30. The first component, generated by the high-frequency digital signal generator HF 28, is an HF digital component, typically with a frequency greater than approximately 100 kHz for an application to multiphase flow imaging, and greater than 15 kHz for corrosion / erosion imaging, for driving the piezoelectric transducer (misusedly called an “acoustic electrode”), and the second component, generated by the low-frequency digital signal generator BF 30, is an BF digital component, typically with a frequency less than 100 kHz, dedicated to driving the resistive electrodes.

[0169] As the two excitation and measurement elements (described below) are used at the same time, and to avoid duplication of the digital system, one for the piezoelectric transducer and the other for the resistive electrode, the outputs of the two digital generators 28 and 30 are digitally pooled via a signal mixer delivering an output signal such that Vout = Vbf + Vhf.

[0170] Such a mixer, making it possible to share the outputs of the two digital generators 28 and 30, corresponds for example to a simple digital signal adder, as shown in [Fig.2].

[0171] When, as shown in [Fig.2], the outputs of the two digital generators 28 and 30 are generated and added digitally, they supply the output of the digital stage 22 by means of a digital-analog converter adapted to the desired performance.

[0172] Depending on the specifications of the excitation and measurement elements used, the digitally generated signal at the output of the digital stage 22 is suitable for being used to drive analog stages (i.e. signal conditioner) as illustrated by [Fig.2], or, as illustrated by [Fig.3] to drive the excitation and measurement elements directly.

[0173] It should be noted that the digital stage 22 also comprises a reception part 32 suitable for digitizing (i.e. digitizing) an analog return signal from said two excitation and measurement elements via a very high-performance analog-to-digital converter 34 whose sampling frequency is at least twice as high as that of the analog return signal from said two excitation and measurement elements, and for discriminating it in the Fourier space via a discrimination tool 36 using at least one Fourier transform, in particular a fast Fourier Transform (FFT). More precisely, such a very high-performance analog-to-digital converter is suitable for being integrated into the processor or an external component. Its purpose is to have a very high sampling frequency: at least twice as high as the frequency of the highest signal according to Nyquist, as well as good precision allowing perfect execution of the algorithms. The digitized signal is composed of several frequency components will be digitally processed in order to supply the processing carried out by the electronic signal generation and acquisition device 16 and / or by the tomographic imaging device 18 with the necessary information.

[0174] According to one example, the digital stage 22 is suitable for being shared for a set of sensors. For example, for sixteen sensors, the same digital stage 22 is used to provide the transmission with a matrix of 16 x 16 signals = 256 two-component signals (corresponding to the 256 pairs of sensors). For the transmission part of such a digital stage 22, a multiplexer makes it possible to choose on which transmission channel(s) the signal is transmitted. In reception, all the sensors are suitable for measuring simultaneously in order to save time.

[0175] As indicated previously, the voice corresponding to the acoustic emission can be cut on the reception side (i.e. via an open switch controlled by a dedicated signal) to prevent a high voltage (100V for example) from rising to the acquisition card which is not necessarily capable of receiving such high voltages.

[0176] According to one example, there is one analog stage 24 per sensor.

[0177] The analog stage 24 comprises a transmission part 38.

[0178] According to the example of [Fig.2], the excitation signals of the two elements excitation and measurement arrive through the same channel corresponding to the output of digital stage 22.

[0179] Within the transmission part 38 of the analog stage 24, the HF analog component is optionally separated from the LF analog component via an optional high-pass filter 40 with a cutoff frequency relatively far from the frequencies used to generate the electrical component (LF part) of the aforementioned two-component signal. This HF analog component obtained at the output of the optional high-pass filter 40 is used to excite the piezoelectric transducer, and is capable of having a very high impedance and excitation voltages with relatively high levels (e.g. of the order of several tens of volts), hence the need, in this case, for a voltage amplifier 42 before exciting the piezoelectric transducer described below.

[0180] Within the transmission part 38 of the analog stage 24, the analog BF component is separated from the analog HF component via a low-pass filter 44 in order to be used to excite the resistive electrode described later. This analog BF component obtained at the output of the low-pass filter 44 is capable of having a very low impedance, hence the need to use a current amplifier 46. Some systems have impedances close to zero (a few mOhm) and require the use of a current amplifier greater than 100 amps for be able to generate excitation signals of a few hundred mVolt. This type of amplifier 46 can be a simple operational amplifier stage A, B or AB or an H bridge system (i.e. class D amplifier). The resulting current is measured at the output of the amplifier 46 in voltage via a shunt 48 (in English current sensor) introduced in series in the excitation circuit.

[0181] In other words, the transmission part 38 of the analog stage 24 comprises, according to the embodiment of [Fig.2], a low-pass filter 44 and an optional high-pass filter 40 configured to separate, within said two-component analog excitation signal provided by the transmission part 26 of the digital stage 22, the electrical excitation component from the acoustic excitation component.

[0182] The two excitations delivered respectively at the output of the optional voltage amplifier 42, and after passing through the shunt 48 are supplied to a device for emitting and measuring electric and acoustic waves 50 as such, for example for imaging a flow pipe 52, for example a metal tube.

[0183] In Figures 2 to 5, a pair of sensors is shown, each sensor comprising a piezoelectric transducer 54 and a resistive electrode 56. For the sake of simplicity, only one of the sensors of the pair is excited, but it is obvious that the two sensors are capable of being excited in a similar manner, in particular when they operate in transmission mode or in transmission and reception mode.

[0184] According to a variant not shown, said two-component signal at the output of the digital stage 22 is directly supplied as such to the piezoelectric transducer 54, which makes it possible to dispense with the optional high-pass filter 40 and the voltage amplifier 42. In other words, this variant makes it possible to simplify the electronics, since the optional high-pass filter 40 and the voltage amplifier 42 are not necessary, and consequently limits the cost of the system while being able to couple to all types of reception. Indeed, as indicated previously, it does not pose a problem to send the entire two-component signal (i.e. both components at the same time) to the PZT piezoelectric transducer 54 of the sensor because the low-voltage, low-frequency electrical component of the two-component signal will attenuate throughout the propagation and will thus not be measured by the receiver, which will therefore not disturb the measurement.

[0185] Furthermore, it should be noted that for all of the variants illustrated by figures 2 to 5, the transmission part 38 of the analog stage 24 is at least capable of adapting the impedance and / or the amplitude of said two-component analog excitation signal provided by the transmission part 26 of the digital stage 22, respectively by means of a current amplifier 46 and / or an optional voltage amplifier 42.

[0186] Indeed, the transmission part 26 of the digital stage 22 generates signals with a relatively high impedance and with low amplitude voltages. In the case where the impedance is not matched, a current amplifier is therefore required. In the case where the amplitude is not matched, a voltage amplifier is also required.

[0187] The transmission signals conditioned by the amplifiers 42 and 46 directly and respectively supply the excitation and measurement elements 54 and 56.

[0188] The analog stage 24 also comprises a reception part 58 suitable for forming an analog return signal from said two excitation and measurement elements and comprising at least the current measurement tool 48 used to measure the current of the electrical signal delivered by the resistive electrode 56 dedicated to the tomographic measurement by electrical impedance, and a pre-amplification tool 60 configured to adapt the impedance and amplify the amplitude of the signal delivered by the piezoelectric transducer 54 dedicated to the acoustic tomographic measurement.

[0189] As an optional addition, as illustrated by the embodiment of [Fig.2], the receiving part 58 of the analog stage 24 further comprises a variable gain amplification tool 62 whose input is connected to the output of the pre-amplification tool 60.

[0190] As an optional addition, the reception part 58 of the analog stage 24 further comprises a mixer of the signal delivered by the current measurement tool 48 and of the signal delivered by the pre-amplification tool 60 or respectively by the variable gain amplification tool 62.

[0191] In other words, the receiving part 58 of the analog stage 24 is such that for the resistive electrode 56, the return is made by measuring the current via the shunt 48. The current of each resistive electrode is measured. Within the shunt 48, the signal generated by a resistor placed in series or a current transformer is conditioned by an amplifier in order to adapt it to the digital measurement range. In other words, the potential is generated on the shunt 48 / electrode circuit (i.e. the current is measured on the shunt 48).

[0192] The piezoelectric transducer 54 in reception mode generates a low amplitude voltage signal. The pre-amplification stage (i.e. the tool) 60 is used to adapt the impedance and amplify the amplitude of the signal. A second variable gain amplification (PGA) stage 62 is optionally used to avoid saturation of the received signal.

[0193] Thus, the present invention also proposes a sensor design solution comprising analog and digital electronics for generating simultaneous signals to power the excitation and measurement elements dedicated respectively to electrical impedance tomography and acoustic tomography, and analog and digital electronics for receiving simultaneous signals from these excitation and measurement elements dedicated respectively to electrical impedance tomography and acoustic tomography, and to reconstruct separate data matrices for electrical and acoustic tomography.

[0194] As an alternative illustrated by [Fig.3], the acousto-electric tomography sensor has an architecture 64 different from the architecture 20 of [Fig.2], this architecture 20 of [Fig.2] being, to summarize, based on the digital generation of the digital HF and LF components, added digitally and supplied within a single output channel from the digital stage 22 to the analog stage 24, then analogically filtered to subsequently excite separately respectively the piezoelectric transducer and the resistive electrodes.

[0195] According to the architecture 64 of [Fig.3], the digital HF and LF components are still generated digitally, by the digital signal generators 28 and 30, but supplied simultaneously (in particular via a trigger, not shown, from the English trigger) on two separate output channels from the digital stage 22 to the analog stage 24, suitable for directly respectively supplying the voltage amplifier 42 dedicated to the HF component and the current amplifier 46 dedicated to the LF component.

[0196] The architecture 64 of [Fig.3] allows, at the cost of two separate output channels from the digital stage 22 to the analog stage 24 instead of one output channel according to the architecture 20 of [Fig.2], to eliminate the digital adder and the two analog filters 40 and 44 used according to the variant 20 of [Fig.2] to separate the two HF / LF components in analog.

[0197] The architecture 64 of [Fig. 3] is for example implemented in the case where the excitation of the piezoelectric transducer 54 is done at a fixed amplitude, so that a digital signal, for example a square signal of adapted and predetermined frequency, at the output of the digital stage 22 is capable of directly supplying the voltage amplifier 42 dedicated to the HF component making it possible to eliminate the two analog filters 40 and 44 used according to the variant of [Fig. 2] to separate the two HF / LF components in analog.

[0198] Another variant of the embodiment of [Fig.3], illustrated by [Fig.4], is implemented in the case where additional analog digital channels are available, so that the reception part of the analog stage can be simplified by removing the “+” adder of [Fig.3] allowing the signals to be mixed.

[0199] [Fig.5] presents yet another variant 68 where although the signal generation and acquisition chains operate simultaneously, as in [Fig.2], it is not excluded to operate the acoustic and electrical tomography independently with adjacent excitation and measurement elements 56 and 54. or even on different measurement areas.

[0200] [Fig.6] shows three different arrangements of the two excitation and measurement elements constituting the acousto-electric tomography sensor proposed according to the present invention.

[0201] According to a first arrangement shown on a surface 70 of [Fig.6] and as also illustrated by [Fig.2] to 4, said resistive electrode 72 dedicated to the tomographic measurement by electrical impedance and said piezoelectric transducer 76 dedicated to the acoustic tomographic measurement are superimposed and form a stack while being separated from each other within said stack by an electrically insulating layer 74. With respect to the structure and / or the flow to be imaged by tomographic measurement, represented by the surface 70, within said stack, the resistive electrode 72 dedicated to the tomographic measurement by electrical impedance being the proximal excitation and measurement element, and said piezoelectric transducer 76 dedicated to the acoustic tomographic measurement being the distal excitation and measurement element.

[0202] Indeed, the acoustic signal emitted following excitation of said piezoelectric transducer 76 is able to pass through the resistive electrode 72, but not the reverse due to the insulating layer 74 which does not disperse the acoustic waves.

[0203] According to a second arrangement shown on a surface 78, and as also illustrated by [Fig.5], the two excitation and measurement elements 80 and 82, respectively acoustic and electrical, are arranged so as to be independent of each other. In other words, according to this second arrangement, said resistive electrode 82 dedicated to the tomographic measurement by electrical impedance and said piezoelectric transducer 80 dedicated to the acoustic tomographic measurement are adjacent and separated within said sensor.

[0204] According to a third arrangement represented on a surface 84, said piezoelectric transducer 86 dedicated to acoustic tomographic measurement and said resistive electrode 88 dedicated to electrical impedance tomographic measurement are arranged concentrically, said electrode dedicated to electrical impedance tomographic measurement 88 surrounding said piezoelectric transducer dedicated to acoustic tomographic measurement 86.

[0205] According to a particular and optional aspect, specifically for an application to the imaging of a two-phase water / air flow in the nuclear field, the present invention also relates to a smart flange for the acousto-electric tomographic measurement of such a two-phase flow of an installation conduit, the flange comprising at least one pair of acousto-electric sensors of the aforementioned type, namely comprising two distinct excitation and measurement elements, co-located within said sensor, dedicated respectively to the tomographic measurement by electrical impedance and to the acoustic tomographic measurement, and suitable for being simultaneously excited via two distinct components of a two-component signal, the electrode dedicated to the tomographic measurement by electrical impedance being capable of being excited by an electrical excitation component of said two-component signal, and the electrode dedicated to the acoustic tomographic measurement being capable of being excited by an acoustic excitation component of said two-component signal, said sensors being placed in contact with said flow, the flow being two-phase (water / air for example).

[0206] Such a smart flange with integrated sensors in contact with the flow is mainly suitable for metallic structures because otherwise electrical impedance tomography cannot work since these structures are conductive.

[0207] Such a smart flange with integrated sensors is also suitable for tube wall imaging to monitor corrosion / erosion defects as part of structural health monitoring or SHM (Structural Health Monitoring) because today this application requires power electronics for the electrical impedance tomography part.

[0208] As an alternative to the aforementioned smart flange, according to a particular arrangement, the sensors of the network 12 are suitable for being positioned in the form of at least one collar around the structure.

[0209] Furthermore, the present invention also relates to a method, not shown, of acousto-electric tomographic measurement of a body, such as for example the metal tube 52 of FIGS. 2 to 5, comprising a cylindrical part containing a fluid, said method comprising the following steps:

[0210] - arrangement of a network of acousto-electric tomography sensors comprising at least one pair of acousto-electric tomography sensors according to the present invention, said at least one pair comprising a sensor in transmission mode and a sensor in reception mode;

[0211] - simultaneous excitation of each of the two excitation and measurement elements of each sensor in emission mode by a two-component signal V^t) = VT(0 + :

[0212] - said excitation and measurement element dedicated to tomographic measurement by electrical impedance being excited by the potential; ( / ) — sin ( 2trf t ), where Ae represents the excitation signal amplitude of said excitation and measurement element dedicated to electrical impedance tomographic measurement and fe its excitation frequency,

[0213] - said excitation and measurement element dedicated to acoustic tomographic measurement being excited for example by the signal ( t ) corresponding to n cycles of sinusoid windowed by a Hann window:

[0214] yexc j Vre^O, yj Vf^t) =0 V?eÀ\[o, L p.

[0215] where Ap represents the excitation signal amplitude of said excitation and measurement element dedicated to acoustic tomographic measurement, the index p representing the piezoelectric term, fp its central excitation frequency and ncy the number of sinusoid cycles of said signal Ve? c ( t ) \

[0216] - periodic acquisition of electrical data y^^ — y"*™ + of said bodies obtained using the two excitation and measurement elements of each sensor in reception mode of a pair of index n from the sensor network,

[0217] - processing of said electrical data = Ve*™ + V'p^ comprising:

[0218] - for each excitation and measurement element dedicated to tomographic measurement by electrical impedance the calculation of the Mn data points defined by: 102191 =

[0220] where R is the value of the resistance used for the measurement of V”'^ with V”*™ = RL across the resistor, P is the number of points in a discrete sequence of measurement of the current In, p is the discrete time, k is a coefficient associated with the frequency fe and [3P = (2irp / P), and optionally in the case of using frequency division multiplexing according to the aforementioned COLTRANE method, the data points Mn(k) are relative to the multi-frequency signals of frequency fk with k the set of coefficients Fourier efficiencies of multi-frequency excitation signals;

[0221] - for each excitation and measurement element dedicated to tomographic measurement acoustics the calculation of the Mn data points defined by: M,p) ^yV'r^P^] where l is a coefficient associated with the frequency fp

[0222] - constitution of two data matrices De and Dp from said data points Mn( k) and Mn( I) for all n, k and 1.

[0223] Figure 7 illustrates in time and frequency the acousto-electric signal capable of being generated according to the present invention such that ( f ) — ( f ) + (0 -P'us precisely in [Fig.7] an example of such a two-component signal is represented in particular in view 90 where the electrical component 92 and the acoustic component 94 are represented separately, while view 96 illustrates the resulting two-component signal. In particular, according to the example of [Fig.7], the acoustic component 94 corresponds in particular to five sinusoid cycles windowed by a Hann window.

[0224] For reasons of practicality in the representation of [Fig.7], the difference in The amplitude between the electrical component 92 and the acoustic component 94 is quite low and the same is true for the working frequency (90V at 150 kHz for the acoustic component 94 and 20V at 10 kHz for the electrical component 92). In practice, it would be closer to 100V at 150kHz for the acoustic component and IV at 1 kHz for the electrical component.

[0225] It should be noted that in the case where optionally a frequency division multiplexing is used the two-component signal yext (t) = Ve™(0 + (t) then becomes

[0226] y^caJ^cos(Tjtfmt) [&os(mO„) + 5®sin (^ ) ] + ( *)

[0227] where 0n is the angular position of the electrode of index n, ô the Kronecker delta, O the set of positive odd numbers, E the set of positive even numbers minus 0, fm = m * f0 is an oscillation frequency, fo is a fundamental frequency chosen such that fm is less than the Nyquist frequency of the system for all m.

[0228] According to an optional aspect, a simultaneous excitation strategy for acoustic tomography can also be envisaged if the signals are discriminable at the acquisition stage.

[0229] View 98 illustrates the frequency spectrum associated with the two-component signal of the time view 96. Such a spectrum 98 advantageously comprises two distinct frequency supports, namely a first electrical frequency component 100 and a second acoustic frequency component 102. These two frequency supports 100 and 102 are separate, which advantageously makes it possible to separate the electrical information from the acoustic information once the measurements have been carried out.

[0230] It should be noted that the wave packet of five sinusoid cycles windowed by a Hann window of the acoustic component 94 represented temporally on the view 90, corresponds on the frequency view 98, to an acoustic frequency component 102 whose spectral band is wide compared to that of the monochromatic electrical frequency component 100, hence the term “wide band” associated with the acoustic excitation component.

[0231] As an optional addition, the method further comprises a step of generating an image by reconstruction according to the classic inverse iterative least square method applied, specifically according to the present invention, to the two data matrices De and Dd or to a combination of these two matrices.

[0232] Such a tomographic measurement method therefore essentially consists of implementing frequency multiplexing in which the excitation signals are imposed simultaneously on all the excitation and measurement elements. To enable discrimination of the signals in Fourier space, each excitation and measurement element, resistive electrode and piezoelectric transducer, is excited by a signal of sinusoidal shape.

[0233] In addition, such a method thus makes it possible to process excitation signals and measurements simultaneously in time and space to produce coupled acoustic and electrical impedance tomography images. This makes it possible to take advantage of the advantages of both methods by mutually complementing their weak points. Thus, it is possible to cover a wider range of multiphase flows in a de-flowmetry context or to expand the number of processable configurations for corrosion / erosion imaging in metallic structures.

[0234] The invention also relates to a computer program comprising software instructions which, when executed by a computer, implement such a method of acousto-electric tomographic measurement of a body comprising a cylindrical part containing a fluid.

[0235] Those skilled in the art will understand that the invention is not limited to the embodiments described, nor to the particular examples of the description, the embodiments and variants mentioned above being suitable for being combined with each other to generate new embodiments of the invention.

[0236] Thus, the present invention proposes different elements, namely an electronic signal generation and acquisition device 16, and / or a network 12 of sensors, and / or a method and a computer program which independently, or combined within the same system, each contribute to carrying out simultaneous measurements in time and space of acousto-electric tomography, acoustic tomography and electrical impedance tomography being complementary, their simultaneous deployment according to the present invention mutually overcomes the shortcomings of their separate use.

[0237] It should be noted that the electronic signal generation and acquisition device 16 which makes it possible to obtain simultaneity in time is suitable for being combined with sensors other than those described within the present invention, insofar as these sensors make it possible to obtain simultaneity in space for the two tomography techniques, namely electrical impedance tomography and acoustic tomography.

[0238] Conversely, the acousto-electric sensors of the network 12, one embodiment of which is described in relation to FIGS. 2 to 6, make it possible to obtain simultaneity in space and are suitable for being combined with another electronic device for generating and acquiring a signal than that described within the present invention, insofar as this electronic device for generating and acquiring a signal makes it possible to obtain simultaneity in time, namely for electrical impedance tomography and for acoustic tomography. According to another variant described within the present application, the acousto-electric sensors of the network 12 themselves incorporate electronics comprising a digital part and an analog part capable of intrinsically providing said simultaneity in time.

[0239] Advantageously, according to the present invention, the same sensors (CE as CR) and the same signal processing electronics for the acoustic part and for the electrical part (transmission and reception) are used. The acousto-electric tomography sensors comprise both piezoelectric transducers (PZT) and resistive electrodes, a sensor structure capable of advantageously providing simultaneity in time and space subsequently making it possible to combine the images and thus to benefit from the advantages of the two imaging methods by electrical impedance tomography and by acoustic tomography, the complementarity of which makes it possible, for example, to have faithful imaging of the two-phase flow regardless of the void ratio.

[0240] In terms of scanning speed, electrical impedance tomography allows rapid acquisitions of large inclusions which in acoustic tomography may on the contrary require scanning with low frequencies and therefore a significant acquisition time, a problem advantageously eliminated when the two methods are coupled according to the present invention.

[0241] Furthermore, the reconstruction of images from acousto-electric data involves perfectly superimposable images in the context of flows. The present invention proposes different elements 12, 14, 16 and 18 and also a method for obtaining a superposition in time and space to have identical boundary conditions and reconstruct superimposable images of electrical impedance tomography on the one hand and acoustic tomography on the other hand.

[0242] By coupling electrical impedance tomography and acoustic tomography, the present invention thus makes it possible to solve two technical problems associated respectively with the imaging of multiphase flows, and with the imaging of corrosion / erosion (e.g. loss of thickness) in thin metal structures (e.g. plates and tubes).

[0243] In particular, the efficient coupling of electrical impedance tomography and acoustic tomography makes it possible to achieve: a wide range of measurable void ratios, namely from 105 (0.001%) to 10° (100%), uniformity of measurement sensitivity by being more sensitive both at the edge and at the center of the measurement domain, a high image rate, necessary for flow measurement.

[0244] Furthermore, thanks to this coupling, the slow low-frequency scanning of acoustic tomography for large inclusions is replaced by a very fast electrical impedance tomography scanning, this last point being important also for the reconstruction of the images which will consider the data coming from the two measurements com- additional.

[0245] Such coupling is advantageously applicable to imaging in multiphase flow pipes in the “Oil & Gas”, nuclear, agricultural, agri-food, chemical, etc. sectors, to imaging of mixtures / separations, chemical processes in the pharmaceutical, chemical, etc. sectors, to imaging for the detection of foreign bodies in the agricultural, agri-food, cosmetic sectors, to imaging in metallic environments, such as for cables, tubes, furnaces, conduits, etc., imaging in heat exchangers, imaging in pumps, imaging in engines, injectors, fuel cells, imaging of corrosion erosion in pipes or plates in the “Oil & Gas”, nuclear, aeronautical, etc. sectors.

[0246] The proposed technical solution makes it possible to use both acoustic and electrical techniques while keeping the same number of inputs and outputs of the acquisition system thanks to the use of superimposed signals. This innovative solution makes it possible to benefit from the advantages of acousto-electric measurements without significantly complicating the acquisition chain compared to separate acoustic tomography or electrical tomography measurements.

Claims

Claims

1. Electronic device for generating and acquiring an acousto-electric tomography signal for structural corrosion / erosion imaging and / or multiphase flow imaging by using a network of acousto-electric tomography sensors, said network comprising at least one pair of sensors (140 to 14N), said pair comprising a transmitter sensor (CE) and a receiver sensor (CR), said device being characterized in that it comprises: - a signal generation module configured to generate, for each transmitter sensor (CE) of each pair of sensors (140 to 14N) of said network, a two-component signal, said two-component signal comprising both an acoustic excitation component and an electrical excitation component mixed together within said two-component signal,- a signal acquisition module configured to: - acquire a signal representative of the signal received by each receiver sensor (CR) of each pair (140 to 14N), and - from said representative signal, to generate two distinct received components respectively dedicated to acoustic tomography and electrical impedance tomography.,

2. A device according to claim 1, wherein said electrical excitation component is a component whose voltage is lower than a first predetermined voltage threshold, and wherein said acoustic excitation component is a component whose voltage is higher than a second predetermined voltage threshold, said second voltage threshold being higher than or equal to said first voltage threshold.

3. The device of claim 2, wherein said first voltage threshold is substantially equal to one volt while said second voltage threshold is substantially equal to one hundred volts.

4. A device according to any preceding claim, wherein said electrical excitation component corresponds to a monochromatic component, and wherein said acoustic excitation component is a broadband component.

5. A device according to any preceding claim, wherein said electrical excitation component is a component whose frequency is lower than a first pre-frequency threshold. determined, and wherein said acoustic excitation component is a component whose frequency is greater than a second predetermined frequency threshold, said second frequency threshold being greater than or equal to said first frequency threshold.

6. A device according to claim 5, wherein, for multiphase flow imaging, said first frequency threshold is substantially equal to 100 kHz while said second frequency threshold is substantially equal to 150 kHz.

7. A device according to claim 5 or 6, wherein, for structural corrosion / erosion imaging, said first frequency threshold is substantially equal to 10 kHz while said second frequency threshold is substantially equal to 20 kHz.

8. Device according to any one of the preceding claims, in which said generation module comprises a mixer having as inputs said acoustic excitation component and said electrical excitation component and as output said two-component signal, said mixer corresponding to an adder.

9. Device according to any one of the preceding claims, wherein said generation module further comprises a set of electronic switches configured to time-division multiplex the acoustic excitation components and / or the electrical excitation components of a plurality of two-component signals, each two-component signal of said plurality being associated with a separate emitting sensor.

10. Device according to any one of the preceding claims, wherein said generation module further comprises a frequency multiplexing tool configured to multiplex in frequency division the acoustic excitation components and / or the electrical excitation components of a plurality of two-component signals, each two-component signal of said plurality being associated with a separate emitting sensor.

11. Device according to any one of the preceding claims, in which the acquisition module comprises: - a predetermined set of band-pass filters, said set of band-pass filters being configured to discriminate, within the signal representative of the signal received by each receiver sensor of each pair, the received component dedicated to acoustic tomography from the received component dedicated to electrical impedance tomography; or - a high-pass filter to recover the received component dedicated to acoustic tomography, and a low-pass filter to recover the received component dedicated to electrical impedance tomography.

12. Device according to any one of claims 1 to 11, in which the acquisition module is capable of applying a predetermined set of Fourier transforms, said set of Fourier transforms being configured to discriminate, within the signal representative of the signal received by each receiving sensor of each pair, the received component dedicated to acoustic tomography from the received component dedicated to electrical impedance tomography.

13. Acousto-electric tomography system for imaging corrosion / erosion of structure and / or multiphase flow imaging, the system being characterized in that it comprises: - a network of acousto-electric tomography sensors comprising at least one pair of sensors, said pair comprising a transmitter sensor and a receiver sensor; - at least one electronic device for generating and acquiring an acousto-electric tomography signal according to any one of the preceding claims, - a tomographic imaging device;the electronic signal generation and acquisition device being capable of: - exciting each emitting sensor of each pair of sensors of said network using said two-component signal, - providing as input to said tomographic imaging device two separate sets of data respectively obtained from the two separate received components respectively dedicated to acoustic tomography and electrical impedance tomography.;

14. The system of claim 13, wherein said tomography device is capable of independently generating: - an acoustic tomography image from the received component dedicated to acoustic tomography; - an electrical impedance tomography image from the received component dedicated to electrical impedance tomography; and of recombining said acoustic tomography image with said electrical impedance tomography image to form an acousto-electric tomography image, or wherein said tomography device is capable of generating di- rectly an acoustoelectric tomography image by processing together the received component dedicated to acoustic tomography and the received component dedicated to electrical impedance tomography, via a predetermined iterative inversion tool, or via a predetermined artificial intelligence tool.

15. System according to claim 13 or according to claim 14, in which each acousto-electric tomography sensor of said network comprises two distinct excitation and measurement elements, co-located within said sensor, dedicated respectively to the tomographic measurement by electrical impedance and to the acoustic tomographic measurement, and capable of being excited simultaneously via two distinct components of a two-component signal, the excitation and measurement element dedicated to the tomographic measurement by electrical impedance being capable of being excited by the electrical excitation component of said two-component signal, and the excitation and measurement element dedicated to the acoustic tomographic measurement being capable of being excited at least by the acoustic excitation component of said two-component signal.

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