Patent Application
20220090955
The present invention relates to the field of measuring the fill level of a fluid tank, and more precisely to the use of acoustic waves to measure the fill level of a fluid tank. Although the present invention can be used in many fields, it finds a particular application in that of refrigeration or air conditioning type facilities, used, non-restrictively, in the field of fresh and frozen product distribution.
Refrigeration and air conditioning type systems are indeed supplied with fluids that are stored in part in pressurized tanks, which are generally opaque and closed.
A system for measuring the liquid fill level of a tank is known in prior art from patent application FR2949559A1, making it possible to give the value of this level instantaneously, whatever the shape of the tank, orientation of the tank (vertical or horizontal) and nature of the liquid it contains, while being reliable and inexpensive. This measurement device comprises a vertically arranged external column connected to the tank through flexible pipes. According to the principle of communicating vessels, the level of the liquid balances at the same height in the external column and in the tank. This measurement device further comprises weighing means holding the external column, in order to measure the weight of the external column as a function of the liquid level. This measurement device also comprises a calculator configured to determine the level of liquid in the external column, especially from the measured weight of the external column, and consequently the fill level of the tank. However, this measurement system requires that the tank comprises an upper port and a lower port so that the tank and the external column are in communication. Furthermore, it is necessary to drain the tank when connecting the external column. Since fluids used in refrigeration or air conditioning type systems are also harmful to the environment and/or health, this draining is also delicate to carry out.
To eliminate these drawbacks, the fill level of a fluid tank can be measured non-intrusively using acoustic waves in the ultrasonic range. This measurement is based on differences in physical properties of acoustic waves propagating in two different single-phase fluids, namely a liquid and a gas, two different liquids, or two different gases. As an example, the speed of propagation of an acoustic wave is higher in liquids than in gases. This measurement additionally uses reflection and refraction of acoustic waves. According to these principles, when an acoustic wave propagating in a first single-phase fluid, called an incident wave, meets an interface with a second single-phase fluid, part of the acoustic wave, called a refracted wave, propagates in the second single-phase fluid and the other part, called a reflected wave, propagates in the reverse sense in the first single-phase fluid. It is considered for the following that the first single-phase fluid is a liquid-phase refrigerant, whose fill level is desired to be known, and that the second single-phase fluid is this gas-phase refrigerant, which corresponds to the most common case.
As illustrated in
As illustrated in
As illustrated in
In a similar way, from patent application U.S. Pat. No. 5,755,136A1, there is known the emission of an acoustic wave from a first wall to a second opposite wall in order to measure, on the one hand, the acoustic attenuation over a round trip and, on the other hand, the vibratory response of the first wall. The combined measurements of the acoustic attenuation and the vibratory response allow to determine whether a liquid is present between the first wall and the second wall at the measurement location. Such a method remains complex and time consuming since it requires two independent measurements. Finally, the measurement of acoustic attenuation is inaccurate since the first and second walls are generally not perfectly planar and are far apart.
There is therefore a need for a system and method for measuring the fill level of a fluid tank that is accurate and reliable, independent of the shape and orientation of the tank and independent of the nature of the fluids contained in the tank.
The invention relates to an acoustic wave measurement system for measuring the fill level of a tank, said tank storing a first single-phase fluid having first physical properties and a second single-phase fluid having second physical properties, said first physical properties comprising a first density and said second physical properties comprising a second density strictly lower than the first density so that the single-phase fluids are vertically superimposed in the tank, the first single-phase fluid being located in the lower part of the tank, the second single-phase fluid being located in the upper part of the tank, said first single-phase fluid and said second single-phase fluid being separated by a substantially horizontal interface, said tank comprising an envelope extending longitudinally along an axis, the envelope comprising an inner face in contact with the single-phase fluids and an outer face, the envelope comprising a cylindrical median portion.
The measurement system is remarkable in that it comprises:
Advantageously, by virtue of the invention, each transducer makes it possible to verify the presence of the first single-phase fluid at each height by measuring an acoustic attenuation. Advantageously, the use of a plurality of transducers forms a detection scale in order to determine the interface between the single-phase fluids in a discrete manner.
Unlike prior art which teaches to measure acoustic attenuation directly in a fluid, the present invention is directed to an indirect measurement by analyzing the acoustic attenuation of the wall. Advantageously, the applicant has realized that the acoustic attenuation of the wall depends on the presence or absence of fluid on the inner side of the wall. Indeed when an acoustic wave is reflected on any interface, the fluid located on the other side of the interface absorbs part of the energy of the acoustic wave, thereby decreasing its amplitude. By virtue of the invention, the presence of a fluid is detected independently of the cross-sectional area of the tank, which is highly advantageous.
Preferably, the transducers are aligned along a line in a vertical plane. Advantageously, the transducers are connected with each other so as to facilitate installation and wiring thereof.
According to a first aspect, the transducers are aligned along a rectilinear or straight line, in particular, for a vertical tank.
Preferably, the transducers are configured to emit horizontal incident acoustic waves. This advantageously allows for detection by acoustic energy attenuation. Acoustic energy attenuation refers to an attenuation of the amplitude of the acoustic wave or, in other words, its acoustic power.
According to a second aspect, the transducers are aligned along a curved line but in the same vertical plane for a horizontal tank.
Preferably, the calculation member is configured to determine the state of a transducer from the difference in acoustic energy between the emission of the incident acoustic wave O1 and the reception of the reflected acoustic wave O2 that it has received.
Preferably, the difference in acoustic energy is determined from the acoustic impedance of the single-phase fluids. Preferably, the measurement system comprises a temperature sensor in order to determine the acoustic impedance to be taken into account, which is a function of the temperature of the fluid.
Preferably, the calculation member is configured to compare electric signals to a database comprising reference acoustic attenuations of the single-phase fluids for said tank to determine the presence of the first single-phase fluid at each vertical height of the transducers. More preferably, the calculation member is configured to compare the difference in acoustic energy at each transducer to a database comprising reference acoustic attenuations of single-phase fluids for said tank.
Preferably, with the calculation member configured to determine, for each transducer, a lower state in the presence of the first single-phase fluid or an upper state in the absence of the first single-phase fluid, the calculation member is configured to determine the height of the interface from the height of the two successive transducers, one of which is in a lower state and the other is in an upper state.
According to one aspect of the invention, the transducers are configured to emit, further to the incident wave, a complementary incident wave in the wall of the envelope of the tank, the trajectory of this complementary incident wave being oriented by a measurement angle (3 with respect to that of the incident acoustic wave so as to generate a complementary reflected acoustic wave that is received by a transducer adjacent to the transducer having emitted the incident waves.
Preferably, the calculation member is configured to measure acoustic attenuation at each transducer to a database comprising reference acoustic attenuations of single-phase fluids for said tank and for said measurement angle β.
The invention also relates to an assembly of a tank and a measurement system as previously set forth.
The invention further relates to an acoustic wave measurement method for measuring the fill level of a tank, implemented by means of the measurement system as previously set forth, the method comprising:
Preferably, the transducers are controlled simultaneously.
Preferably, the incident waves belong to the ultrasonic range and are preferably sinusoidal pulses.
The invention will be better understood upon reading the following description, which is given solely by way of example, and referring to the appended drawings given as non-limiting examples, in which identical references are given to similar objects and in which:
It should be noted that the figures disclose the invention in detail to implement the invention, said figures can of course be used to better define the invention if necessary.
With reference to
In the following, the vertical direction is defined as the direction of the axis of gravity and the horizontal direction as the direction perpendicular to the vertical. The terms “low,” “high,” “upper,” and “lower” are determined with respect to the vertical direction.
As illustrated in
The first single-phase fluid F1 has first physical properties P1, especially a first density ρ1, and the second single-phase fluid F2 has second physical properties P2, especially a second density ρ2 strictly lower than the first density ρ1, so that the first single-phase fluid F1 is located in the lower part of the tank 10 and the second single-phase fluid F2 is located in the upper part of the tank 10. The theoretical speeds of propagation V1, V2 of an acoustic wave in the single-phase fluids F1, F2 are also known. As will be set forth later, the tank 10 further comprises a temperature probe (not represented) so as to determine temperature T1, T2 of the fluids F1, F2.
As illustrated in
The tank 10 extends longitudinally along an axis X10 which is, in this first embodiment, horizontal. For the sake of clarity and brevity, a tank having a longitudinal axis extending vertically will be referred hereinafter to as a “vertical tank” and a tank having a longitudinal axis extending horizontally will be referred to as a “horizontal tank”.
With reference to
A system for measuring the fill level NR of the tank 10 according to the invention will now be set forth with reference to
In this example, the measurement system 20 comprises a plurality of transducers 22a-22g positioned on the tank 10 at different vertical heights as well as a control member 21 and a calculation member 23 which are connected to the transducers 22a-22g.
Each transducer 22a-22g is configured, on the one hand, to emit, upon receiving a first electric signal U1, an incident acoustic wave O1 to the outer face 12 of a wall of the envelope 11 and, on the other hand, to emit a second electric signal U2, upon receiving a reflected acoustic wave O2, corresponding to the reflection of the incident acoustic wave O1 on the inner face 14 of said wall, the reflected acoustic wave O2 having passed only through the wall of the envelope 11, the second electric signal U2 being a function of the difference in acoustic energy between the incident acoustic wave O1 and the reflected acoustic wave O2. In other words, unlike prior art which teaches to measure the acoustic attenuation in a fluid between the walls of the envelope 11, the present invention suggests to focus only on the acoustic attenuation of the wall of the envelope 11, that is, within the wall thickness. The reflected acoustic wave O2 is received faster than in prior art and has a greater acoustic power, which facilitates its processing since it traveled a shorter distance. This significantly increases accuracy.
Unlike prior art which teaches to measure acoustic attenuation directly in a fluid, the present invention is directed to an indirect measurement by analyzing the acoustic attenuation of the wall of the envelope 11. Advantageously, the applicant has realized that the acoustic attenuation of the wall of the envelope 11 depends on the presence or absence of fluid on the inner face 14 of the wall. Advantageously, each transducer 22 is of the piezoelectric type and allows an electric signal to be converted into a mechanical stress (vibration) and vice versa. However, other types of transducers 22a-22g could of course be used, for example, PZT ceramics, PVDF polymers, etc. Preferably, the incident acoustic wave O1 is a sinusoidal pulse.
Each transducer 22a-22g thus enables the acoustic attenuation between the incident wave O1 and the reflected wave O2 to be measured through the inner face 14 of the wall of the envelope 11.
As will be set forth later, the calculation member 23 is configured to determine, from the electric signals U1-U2 and the physical properties P1-P2 of the single-phase fluids F1, F2, the presence of the first single-phase fluid F1 at each vertical height of the transducers 22a-22g and to deduce the fill level NR therefrom.
The transducers 22a-22g are positioned at different vertical heights so as to detect the presence of the first single-phase fluid F1 at different heights and thereby deduce the fill level NR therefrom. Advantageously, the number of transducers 22a-22g is chosen as a function of the accuracy desired. The transducers 22a-22g are positioned in contact with the outer face 12 of the cylindrical portion 13 of the envelope 11 so as to optimally emit/receive into the wall of the envelope 11.
The control member 21 is in the form of a calculation unit configured to emit the first electric signal U1 at predetermined times. For this purpose, the control member 21 comprises a clock.
In a similar manner, the calculation member 23 is in the form of a calculation unit configured to receive the second electric signal U2 and to determine the time of reception. For this purpose, the calculation member 23 comprises a clock.
Preferably, the control member 21 and the calculation member 23 are integrated in a same calculation module, for example, an electronic board. Preferably, the calculation module comprises a battery for powering the control member 21, the calculation member 23 and the transducers 22.
Preferably, the measurement system 20 further comprises a communication unit for communicating, in a wired or wireless manner, the fill level NR which has been determined. This is particularly advantageous when the measurement system comprises a signaling device as disclosed in patent application FR1871656.
Preferably, the measurement system 20 comprises a flexible support to which the transducers 22a-22g are mounted. This allows the transducers 22a-22g to be accurately positioned with respect to each other, thereby improving the accuracy of the measurement of the fill level NR. Preferably, the flexible support is connected to the tank by bonding, magnetization, or the like.
The calculation member 23 is configured to determine the presence of the first single-phase fluid F1 at each vertical height of the transducers 22a-22g from electric signals U1, U2 from each transducer 22a-22g. Thereafter, when a transducer 22a-22g detects the presence of the first single-phase fluid F1, it is considered to be in a lower state ET1, (presence of fluid) while it is considered to be in an upper state ET2 otherwise (absence of fluid).
Thus, the calculation member 23 makes it possible to define a first group of transducers in the lower state ET1, and a second group of transducers in the upper state ET2. The calculation member 23 can thus conveniently and quickly deduce the interface height I at the interface between both groups of transducers. The height of interface I is higher than any transducer 22 in the lower state ET1 (presence of fluid) and lower than any transducer 22 in the upper state ET2 (absence of fluid). In this example, with reference to
In the first embodiment of
Preferably, the transducers 22a-22g are advantageously equidistant from each other so that the fill level NR of the tank 10 can be determined with an accuracy calibrated to the pitch of the transducers 22a-22g. The density of transducers 22 could of course be higher near certain critical fill levels.
In this example, the transducers 22a-22g are aligned along a single plane transverse to the axis X10 of the tank 10 but, of course, in a second configuration, they could extend along a plurality of transverse planes. In particular, the transducers 22a-22g may extend along two transverse planes spaced apart by the order of the size of a transducer 22a-22g and distributed in a staggered manner so that each transducer 22a-22g has a different vertical position. Such an arrangement is advantageous for possessing significant accuracy without being limited by the dimensions of a transducer 22a-22g. Thus, the accuracy can be higher than the size of the transducer 22a-22g.
As illustrated in
Reflected acoustic waves O2 are generated by reflection of the incident acoustic waves O1 on the inner face 14 of the emission wall and propagate in an identical direction but reverse sense to that of the incident acoustic waves O1 as illustrated in
An example of an implementation of a method for measuring the fill level is shown in
According to the invention, the incident acoustic waves O1 propagate only in the wall of the envelope 11 in the direction normal to the plane tangent to the outer face 12. In other words, the incident acoustic waves O1 propagate in the thickness of the wall of the envelope 11. The reflected acoustic waves O2 are generated by the reflection of the incident acoustic waves O1 on the inner face 14 of the wall of the envelope 11 and propagate in an identical direction but reverse sense to that of the incident acoustic waves O1 as illustrated in
As an example, each transducer 22a-22g is a piezoelectric having a diameter of 10 mm, preferably between 5 mm and 20 mm. Each transducer 22a-22g has a frequency between 0.5 MHz and 2 MHz, preferably in the order of 1 MHz. The amplitude is between 1 and 50V, preferably in the order of 10V. Preferably, the emission steps are spaced from 10 to 100 ms, preferably, in the order of 20 ms.
As an example, with reference to
The calculation member 23 makes it possible to determine the state ET1/ET2 of a transducer 22 from the difference in acoustic energy between the emission of the incident acoustic wave O1 and reception of the reflected acoustic wave O2 that it has received. In other words, the calculation member 23 determines the acoustic attenuation Att corresponding to the reflected energy divided by the incident energy as illustrated in
In practice, the calculation member 23 is configured to compare the difference in acoustic energy at each transducer 22 to a database comprising reference acoustic attenuations of the single-phase fluids F1 F2 for said tank 10.
In this example, the reference acoustic attenuations of the single-phase fluids F1, F2 are determined empirically or theoretically from the acoustic impedances Z1, Z2 of the single-phase fluids F1, F2, size of the tank 10, thickness of its envelope 11, nature of its envelope 11, etc. Preferably, during the installation of the measurement system 20, reference acoustic attenuations of the single-phase fluids F1, F2 are determined by the installer, for example, during a calibration phase.
More precisely, the state ET1/ET2 of a transducer 22 is determined from the amplitude attenuation of the reflected acoustic wave O2 that it has received with respect to that of the incident acoustic wave O1 that it has emitted. Indeed, when an acoustic wave is reflected on any interface, the fluid located on the other side of the interface absorbs part of the energy of the acoustic wave, which decreases its amplitude. The part of absorbed energy depends on the resistance of the fluid, that is its acoustic impedance, and differs for two different single-phase fluids.
In practice, the acoustic impedances Z1, Z2 of the single-phase fluids F1, F2 are calculated from the physical properties P1, P2 of the single-phase fluids F1, F2, that is, their theoretical densities ρ1, ρ2, their theoretical speeds of propagation V1, V2 and their temperatures T1, T2, measured in the tank 10. However, of course the acoustic impedances Z1, Z2 of the single-phase fluids F1, F2 can be obtained in a different way. In this example, the temperatures T1, T2 are measured by a temperature sensor and transmitted to the communication unit connected to the calculation member 23. Preferably, the step of determining the acoustic impedances Z1, Z2 is repeated periodically as the temperatures T1, T2 of the single-phase fluids F1, F2 change over time.
The acoustic attenuation is determined according to the following formula:
Att=(Z2−Z1)2/(Z2+Z1)2 [Math. 1]
In practice, in the presence of a first single-phase fluid F1 which is liquid, the reflected acoustic energy is in the order of 97%. Conversely, in the presence of a second single-phase fluid F2 which is gaseous, the reflected acoustic energy is in the order of 99.8%.
Advantageously, the acoustic attenuation measured at the lowest positioned transducer 22a can be equated to the acoustic attenuation of the first single-phase fluid F1. Similarly, the acoustic attenuation measured at the highest positioned transducer 22g can be equated to the acoustic attenuation of the second single-phase fluid F2. These acoustic attenuations are obtained by a calibration step. Preferably, the calibration step is repeated periodically since the impedances are a function of the temperatures T1, T2 of the single-phase fluids F1, F2 which change over time.
Preferably, the acoustic attenuation is calculated from the reflected energy received by the transducer having emitted the incident wave O1. As illustrated in
Still referring to
Preferably, the measurement angle β is between 1° and 15° so as to allow the interface I to be accurately detected between two transducers 22e-22d having different states ET1/ET2. This advantageously allows to determine whether the fill level NR is closer to the transducer 22d in the lower state ET1, or to the transducer 22e in the higher state ET2. In other words, the accuracy of measurement of the fill level NR is increased by this additional measurement.
Advantageously, the measurement system 20 thus allows a double measurement of the fill level NR of the tank 10, allowing a gain in both accuracy and reliability.
In other words, the reflected energy from an adjacent transducer is measured in order to more accurately determine the interface level I, in particular, when a transducer is located at the interface.
A horizontal tank with an acoustic energy attenuation measurement system has been set forth, but it is understood that such a measurement system 20 is adapted for a vertical tank 10 as illustrated in
As in the case of a horizontal tank 10, of course the transducers 22a-22g may be positioned along a plurality of vertical rectilinear lines, in particular two vertical rectilinear lines spaced apart in the order of one transducer 22a-22g and distributed in a staggered pattern. This has the advantage of being able to arrange a greater number of transducers 22a-22g closer together and thus of increasing accuracy of the measurement.
| Number | Date | Country | Kind |
|---|---|---|---|
| 1900623 | Jan 2019 | FR | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2020/051570 | 1/23/2020 | WO | 00 |
