FR3081049A1 - PIEZOELECTRIC FLOWMETER - Google Patents

Abstract

The piezoelectric flowmeter comprises a duct (4), substantially cylindrical, adapted to circulate a fluid in its interior, a piezoelectric sensor (6), placed around the duct (4), an adapter module (8) connected to the piezoelectric sensor (6). ). In this piezoelectric flowmeter, the piezoelectric sensor (6) is arranged to deform during the passage of the fluid in the conduit (4), so that the electrical signal (110) from the piezoelectric sensor (6) varies continuously with the flow rate. fluid in the conduit (4). The adapter module (8) is arranged to amplify the electrical signal (110) produced by the piezoelectric sensor (6) so that the resulting electrical signal (112) can be operated.

Description

Piezoelectric flowmeter

The invention relates to a piezoelectric effect flow meter.

The complete mapping of the withdrawals in progress on a water supply network (or hydraulic network) is a necessity for all the operators of such networks. These operators know user charges by their meters. But they also need to have a quantified knowledge of authorized and unaccounted direct debits (for example the use of washing outlets (BL) by the municipal road services), as well as unauthorized and unaccounted direct debits. (theft of water) and leaks in the network, in order to be able to react as quickly and precisely as possible to apply countermeasures when it comes to theft or leaks, especially if it is potable water. This point is particularly important for networks located in regions subject to high stress on water resources, where each leak can cause a dramatic waste of water and each flight a consequent loss of income. Finally, these leaks can also lead to a poor evaluation of the work carried out by the network operator, for example by lowering its performance indicators.

The known measuring devices are unsatisfactory. Some only give binary information, for example the triggering of an alarm in the event of the improper opening of a fire hydrant / fire hydrant (PIBI). Others are imprecise and / or not universal, for example a count of the number of turns of a PIBI valve (FR 2 889 871 Al), which must be calibrated and adapted to each PIBI to be able to go back up to 'at debit. Finally, it is known to use a Fourier transform on the signal produced by a piezoelectric band in order to detect leaks in a network (WO 1817/109425 A2) by measuring acoustic vibrations, but this type of device does not allow measure fluid flow.

The present invention improves the situation.

For these purposes, the invention starts from a piezoelectric flowmeter, comprising in a known manner a duct, substantially cylindrical, adapted to circulate a fluid inside, and a piezoelectric sensor, placed around the duct, generating by piezoelectric effect an electrical signal in response to a mechanical stress applied to it, and an adapter module connected to the piezoelectric sensor.

To carry out a measurement of fluid flow by piezoelectric effect, the piezoelectric sensor is arranged to be deformed during the passage of the fluid in the conduit, so that the mechanical stress deforming the piezoelectric sensor varies continuously with the flow of fluid in the conduit . In addition, the adapter module is arranged to amplify the electrical signal produced by the piezoelectric sensor so that the electrical signal obtained can be used.

In other variants, the piezoelectric sensor can:

be a film or a wire, and in an implementation of this variant, the piezoelectric sensor can be wound along its large dimension around the conduit, on its periphery, along a winding line, so that the piezoelectric sensor substantially surrounds the conduit completely, without making a closed electrical loop, comprising polyvinylidene fluoride (PVDF), or being fixed to the conduit by gluing.

In one application, the fluid can be water, in particular drinking water.

The adapter module may further comprise an analog to digital converter, or ADC module, arranged to calculate digital bit rate information from the electrical signal at the output of the amplification module.

This ADC module can also calculate fluid volume information and perform a time stamp.

In a variant, the adapter module also has a temperature sensor communicating a temperature signal to the ADC module.

In one embodiment, the piezoelectric flow meter is arranged to treat fluid flow rates in the range 0-5000 m ³ / h, and / or the range 0-200 m ³ /, and / or the range 0-80 m ³ / h. Alternatively, the piezoelectric flow meter can process fluid flow rates (10) of at least 0.1 lm ³ / h.

The invention also makes it possible to provide a hydraulic network provided with an automated flow measurement, comprising piezoelectric flowmeters arranged on the hydraulic network, and a general controller connected to the piezoelectric flowmeters. The automated flow measurement is carried out by receiving the flow information transmitted by the piezoelectric flow meters, and drawing up a map of the flows and volumes withdrawn from the network.

Finally, the invention provides a method for installing and calibrating a piezoelectric flow meter, which comprises the following operations:

a) fix a piezoelectric sensor around a pipe,

b) install an adapter module near the piezoelectric sensor and connect them electrically, and

c) circulating at different known flow rates a fluid in the conduit to establish a behavioral model, and

d) integrate the behavioral model into the adapter module.

Other characteristics and advantages of the invention will appear on reading the detailed description which follows, relating to examples given by way of non-limiting illustration, as well as on examining the appended drawings, in which:

Figure 1 is a cross-sectional view of the proposed piezoelectric flow meter;

Figure 2 is a longitudinal sectional view of the piezoelectric flowmeter along the plane II-II of Figure 1;

Figure 3 is another side view, from the outside, of the piezoelectric flowmeter, along the plane III-III of Figure 1;

Figure 4 is a detailed view of the architecture of the adapter module 8 of Figures 1 to 3;

FIG. 5 represents, in schematic view, a water network on which the invention can be arranged, and FIG. 6 illustrates an example of a sensor model graph.

The attached drawings essentially contain elements of a certain nature. They can therefore not only serve to better understand the present description, but also contribute to the definition of the invention, if necessary.

In FIGS. 1 to 3, a piezoelectric flow meter 2 comprises a substantially cylindrical conduit 4, a piezoelectric sensor 6, an amplifier-converter module 8 (or adapter module). The piezoelectric sensor 6 can be made of polyvinylidene fluoride (PVDF), at least in part.

The conduit 4 is suitable for a circulation of water 10 inside it. The piezoelectric sensor is in the form of wire or film. It can be wound along its large dimension (or one of them) around the pipe, on its periphery, along a winding line 12, so that the sensor substantially completely surrounds the pipe 4, without making a closed loop . The duct 4 also has a longitudinal direction 14 and a radial direction 16.

The piezoelectric sensor 6 can be fixed by gluing to the duct 4. The gluing advantageously makes it possible to fix the piezoelectric sensor 6 to the duct 4 in a non-intrusive manner, which is both essential for sanitary reasons, and economical for its installation.

When water 10 passes through the conduit 4, hydrodynamic effects induce a pressure which will tend to radially expand the conduit 4. Thus, mechanical stresses are exerted:

- on the duct 4, in the radial direction 16, and

- on the piezoelectric sensor 6, in its longitudinal direction, which follows the winding line 12.

The piezoelectric sensor 6 is wound in order to maximize its sensitivity, that is to say the ratio between the electric current that the piezoelectric sensor will generate and the mechanical stress which is applied to it by deformation of the conduit 4.

The piezoelectric sensor 6 can be arranged so that its main direction, that is to say the direction having the greatest sensitivity to the piezoelectric effect, is parallel to its large dimension. This advantageously makes it possible to increase the measurement sensitivity.

The thickness of the piezoelectric sensor can normally be between 0.1 micrometer and approximately 5 millimeters, for PVDF. This thickness is exaggerated on the drawings, so as to facilitate reading.

By way of example, the Applicant has carried out experiments with a piezoelectric sensor in the form of a wire, of thickness 2 to 3 millimeters. Another type of piezoelectric sensor used by the Applicant included PVDF of nominal thickness 9 to 110 micrometers. Another type of piezoelectric sensor used by the Applicant had a nominal thickness in the range 9-50 micrometers for a strip, and in the range 0.5-lmm for a sheet (“mono oriented sheet”).

Alternatively, the PVDF can be replaced by a copolymer. Its thickness can then be between a few micrometers and 1.2 millimeters.

As said above, the piezoelectric sensor 6 does not form a loop, that is to say that its two ends 18 and 20 do not touch. Thus, the piezoelectric sensor 6 does not form a short circuit.

The adapter module 8 is electrically connected (22) to the two ends of the piezoelectric sensor 6. The adapter module 8 can be arranged, at least in part, on the conduit 4.

The adapter module 8 can be disposed on the conduit 4, and offset in the longitudinal direction 14 of the conduit 4 relative to the piezoelectric sensor 6. The adapter module 8 can also be disposed between the two ends 18 and 20 of the piezoelectric sensor 6, so optimize the overall dimensions of the system.

In another variant, the adapter module 8 can be placed near the duct 4 but not on the duct 4 in order to facilitate its installation. For example, in the case of a buried pipe 4, it can be deposited in a pipe hole accommodating the pipe 4, and in the case of a pipe 4 in the open air be placed near the pipe 4, either on the ground (if the duct 4 is also placed on the ground) or on a bracket (if the duct 4 is kept away from the ground).

The positions of the adapter module 8 described above are not limiting, and in absolute terms the adapter module 8 can be placed anywhere provided that it remains near the conduit 4 and the piezoelectric sensor 6, at least partially .

The piezoelectric sensor 6 and the adapter module 8 can be confronted with potentially very humid environments. Also the piezoelectric flow meter can be protected by a sealing structure 24 which includes the adapter module 8, the piezoelectric sensor 6, and the portion of conduit 4 on which they are fixed. This sealing structure 24 is not shown in the figures.

Alternatively, the piezoelectric sensor can be designed to be inherently moisture resistant.

As a variant, the piezoelectric sensor 6 can make several turns around the duct 4, to increase the sensitivity of the piezoelectric sensor 6. In order to avoid a short circuit, the piezoelectric sensor 6 can then be covered at least partially with an electrical insulator , then be wound up over several turns. In the case of a piezoelectric sensor 6 in the form of a film, a spiral winding can be provided, and the electrical insulator can then be placed on one of the faces of the film. In the case of a piezoelectric sensor 6 in the form of wire, it is also possible to provide a helical winding having as axis the longitudinal axis 14 of the conduit 4, and then the electrical insulator can be a sheath around the wire.

FIG. 4 represents a detailed view of the architecture of the adapter module 8.

The adapter module 8 can comprise an amplification module 100, a temperature sensor 102, an internal clock 104, an analog to digital conversion module (or ADC module) 106 and a transmission module 108.

The amplification module 100 is connected to the piezoelectric sensor 6, and recovers the electrical signal 110, called the raw signal, generated by the piezoelectric sensor 6 in order to produce an amplified version 112. This amplification operation aims to make the raw signal 110 which can be used, manipulated and transmitted by the following modules. Indeed, the gross current induced by a piezoelectric sensor in the context of the invention is of the order of a few millivolts to a few volts, typically of the order of 10 to 100 mV within the framework of a range of flow rates of 0 -40 m ³ / h in the context of experiments conducted by the Applicant. For such voltages, it may be necessary to be able to make these currents more easily exploitable.

It is known that a piezoelectric sensor 6 is a component which returns an electrical signal 110 (that is to say a voltage-current couple) as a function of a mechanical stress which is applied to it. This electrical signal 110 thus generated can also vary according to the temperature of the piezoelectric sensor, its arrangement and its geometry. The behavior model 114 of the piezoelectric sensor 6 is called the function which takes the above parameters as input (mechanical stress, geometry, temperature, material used for the piezoelectric sensor) and which outputs an electrical signal 110 (in voltage and / or in intensity). ). This model 114 is obtained before operating in a network the piezoelectric flow meter 2, by a calibration operation, as will be seen below.

The amplified signal 112 thus obtained can now be used. In particular, the amplified signal 112 at the output of the amplification module 100 can then be sent to the ADC module 106, which will convert this amplified signal 112 into digital bit rate information 116 using the behavioral model 114.

The adapter module 8 can be provided with an internal clock 104 which transmits a clock signal 118. This clock signal 118 can be transmitted to the ADC module 106, which can thus time stamp the digital bit rate information 116.

The temperature sensor 102 is placed against the duct 4, near or on the piezoelectric sensor 6. The advantage of such a temperature sensor 102 is that it can integrate the temperature in the model 114. The temperature sensor transmits a signal temperature 120 at the ADC 106 module. This temperature signal 120 can be analog or digital.

The ADC module 106 can also also calculate fluid volume information (10).

The digital flow information 116 can then be sent to the transmission module 108. The transmission module 108 can then transmit (122) this flow information 116 from flow meter to one or more controllers external to the piezoelectric flow meter 2, as is will see below. This transmission of flowmeter 122 can be done by wire or wirelessly. The transmission module 108 can also transmit other information such as the temperature measured by the temperature sensor 102.

The adapter module 8 can be self-powered, for example with a removable battery. It can also be connected to an electrical network.

It is recalled that any signal which evolves over time is a unique sum of sine and cosine functions, of frequency varying between 0 and infinity. This sum can be obtained by calculating the Fourier transform of the signal, and can be discrete (if the signal is periodic, we then speak of a Fourier series) or continuous (if the signal is not). The term of this sum which is of zero frequency is called the continuous component of the signal.

In the context of the invention, the Applicant is thus interested in the overall deformation of the conduit (expansion), and not in its small deformations (vibrations). Also, in a variant, the adapter module can keep the electrical signal from the piezoelectric sensor at least or only its DC component. This conservation can be achieved by the use of a filter, in particular a low-pass filter. This filter can be analog and / or digital.

FIG. 5 represents a schematic view of a water network 200 on which the invention can be arranged.

A water network 200 comprises one or more catchments 202 which supply one or more water tanks 204. These tanks 204 in turn supply one or more water outlets 206 arranged in a sub-network 208 downstream of a tank 204. The network 200 further comprises one or more piezoelectric flowmeters 2 and at least one general controller 210, which can be installed in a computer. Each pipe in the network can be fitted with a valve 212 (or more).

The piezoelectric flow meters 2 are arranged downstream of the collectors 202, at regular intervals. The piezoelectric flowmeters 2 can be connected by wire and / or wirelessly to the general controller 210 for a flowmeter transmission 122. Thus, the general controller 210 can obtain a multitude of information on the flow rates at different locations on the network 200 and can draw up a map of the network 200. This map can be:

in real time, that is to say that at each instant, the controller has flow information at each point of the network 200 equipped with a piezoelectric flow meter 2, in deferred time, that is to say that the general controller can at any time provide a summary of the average flows and total volumes taken from the network over a sliding time window, for example the last hour, the last day, the last week or the last month, or periodic, that is, the Comptroller General regularly reports on the volumes of water withdrawn since the last report, for example, on the last day or the last month.

This mapping can be used in particular to detect and locate in time and space any anomalies on the network 200, in particular a leak on the network 200 or a theft of water. When an anomaly is detected, the general controller 210 can send an alert message.

Optionally, the piezoelectric flowmeters 2 can be located near the outputs 206 or the valves 212 of the network. As a variant, the piezoelectric flowmeters 2 can be arranged far from the outlets 206 and from the valves 212.

In one implementation, the piezoelectric flowmeters 2 can be arranged on any individual pipe (that is to say a pipe in the network without branching, between two branches) so as to be able to measure the distribution of the flow of fluid at each branch , throughout the network 200.

FIG. 6 represents an example of a sensor model graph 114.

The graph of the sensor model 114 results from experiments carried out by the Applicant. It shows the measured flow rate on the abscissa and the measured mechanical stress on the ordinate (in Newton). The measured flow commonly varies between 0 and 40 m ³ / h. We can go to the range 0-200 m ³ / h (on a PIBI), or even to the range 0

5000 m ³ / h (for a device placed on a transport network, or "feeders"). For washing outlets (BL), we can restrict ourselves between 0 and 5 m ³ / h.

The invention may, as a variant, not measure the low flow rates, and thus be limited to the measurement of flow rates of at least about 100 L / h (that is to say 0.1 m ³ / h). These are typical minimum flows in the case of a washing mouth. In a variant of the invention, the flow rates observed can be at least 0.5 m ³ / h.

The mechanical stress at rest corresponds to the stress along the long dimension of the piezoelectric sensor 6 at rest, when there is no circulation of water 10 in the duct 4. It is non-zero due to the fact that the piezoelectric sensor 6 remains taut, at rest. This mechanical stress at rest is around 10 to 15N in the case of the experiments conducted by the Applicant.

The invention also relates to a method of installation and calibration 300 of a piezoelectric flow meter 2. This method of installation and calibration 300 can comprise the following operations:

a) fix a piezoelectric sensor 6 around a conduit 4, possibly having previously placed an electrical insulator on the piezoelectric sensor 6,

b) install the adapter module 8 near the piezoelectric sensor 6 and connect them electrically (22), and

c) circulating water at different known rates (via an already existing meter) in the conduit 4 to establish a sensor model 114.

Thus, the output of the adapter module (8) represents the flow in the conduit.

This calibration process can be factored in order to save water during the calibration. To this end, steps a) and b) can be carried out several times, at several locations in the network 200, then perform step c) only once to establish all of the sensor models 114. In the context of branches in the part of the network 200 which is being equipped, the distribution (known) of the flows between the different branches can be used in order to establish the sensor models 114 belonging to different branches.

The detailed description above relates to examples given by way of illustration and not limitation.

Thus, a piezoelectric sensor has been described. As a variant, strain gauges can be envisaged.

Claims (14)

, CLAIMS 1. Piezoelectric flow meter (2), comprising: a substantially cylindrical conduit (4) adapted to circulate a fluid (10) therein, a piezoelectric sensor (6), placed around the conduit (4), an adapter module (8) connected to the piezoelectric sensor (6) , characterized in that: the piezoelectric sensor (6) is arranged to deform during the passage of the fluid (10) in the conduit (4), so that the electrical signal (110) from the piezoelectric sensor (6) varies continuously with the flow of the fluid (10) in the conduit (4), and the adapter module (8) is arranged to amplify the electrical signal (110) produced by the piezoelectric sensor (6) so that the obtained electrical signal (112) can be used. 2. Piezoelectric flow (2) according to claim 1, wherein the adapter module is arranged to store the electrical signal from the piezoelectric sensor at least its DC component. 3. Piezoelectric flow meter (2) according to one of the preceding claims, in which the piezoelectric sensor (6) is a film or a wire. 4. Piezoelectric flowmeter (2) according to claim 3, wherein the piezoelectric sensor (6) is wound in its large dimension around the conduit (4), on its periphery, along a winding line (12), so that the piezoelectric sensor (6) substantially completely surrounds the conduit (4), without making a closed electrical loop. 5. Piezoelectric flow meter (2) according to one of the preceding claims, wherein the piezoelectric sensor (6) comprises polyvinylidene fluoride (PVDF). 6. Piezoelectric flow meter (2) according to one of the preceding claims, characterized in that the piezoelectric sensor (6) is fixed to the conduit (4) by gluing. 7. Piezoelectric flow meter (2) according to one of the preceding claims, in which the fluid (10) is water, in particular drinking water. 8. Piezoelectric flow meter (2) according to one of the preceding claims, in which the adapter module (8) further comprises an ADC module (106), arranged to calculate digital flow information (116) from the electrical signal ( 112) at the output of the amplification module (100). 9. Piezoelectric flow meter (2) according to one of the preceding claims, in which the ADC module (106) also calculates information on the volume of fluid (10) and a time stamp. 10. Piezoelectric flow meter (2) according to one of the preceding claims, further comprising a temperature sensor (102) communicating a temperature signal (120) to the ADC module (106). 11. Piezoelectric flow meter (2) according to one of the preceding claims, characterized in that it is arranged to treat fluid flow rates (10) between 0 and 5000m ³ / h, preferably between 0 and 200m ³ / h , and even more preferably between 0 and 80m ³ / h. 12. Piezoelectric flow meter (2) according to one of the preceding claims, characterized in that it is arranged to treat fluid flow rates (10) of at least 0.1 lm ³ / h. 13. Hydraulic network (200), characterized in that it comprises: piezoelectric flowmeters (2) according to one of claims 1 to 11, arranged on the hydraulic network (200), a general controller (210) connected to the piezoelectric flowmeters (2), characterized in that the general controller is arranged for: receiving the flow information (116) transmitted (122) by the piezoelectric flow meters (2), and - draw up a map of the flows and volumes taken from the network (200). 14. Method for measuring flow on a pipe, characterized in that it comprises the following operations: a) fix a piezoelectric sensor (6) according to one of claims 1 to 12 around a conduit (4), b) install an adapter module (8) near the piezoelectric sensor (6) and connect them electrically (22), and c) circulating at different known flow rates a fluid (10) in the conduit (4) to establish a behavioral model (114), and d) integrate the behavioral model (114) into the adapter module (8), so that the output of the adapter module (8) represents the flow in the conduit.