EP2806979A1

EP2806979A1 - Device for nebulizing a liquid

Info

Publication number: EP2806979A1
Application number: EP13704212.3A
Authority: EP
Inventors: Gil Ching; Henri Renggli; Charles Pallanca
Original assignee: Individual
Current assignee: Individual
Priority date: 2012-01-25
Filing date: 2013-01-25
Publication date: 2014-12-03
Also published as: FR2985919B1; WO2013110903A1; US20150076245A1; FR2985919A1

Abstract

The invention relates to a device (100) for nebulizing a liquid, comprising: a vessel (110) that is open at the top portion thereof and configured so as to contain the liquid to be nebulized; at least two ultrasonic-wave generators (120, 130) for emitting at least two ultrasonic-wave fronts (122, 132) into the liquid; and at least two means (134, 124) for focusing the ultrasonic waves, each of which engages with one of said generators (120, 130) in order to concentrate ultrasonic waves at a single point P less than ten millimetres from the free surface of the liquid, wherein the vibration frequencies of the two wave fronts (122, 132) are different.

Description

DEVICE FOR NEBULIZING A LIQUID

FIELD OF THE INVENTION

The present invention relates to a device for nebulizing a liquid. It applies, especially to the nebulization of water. PRIOR ART

The principle of acoustic nebulization is based on the focusing of an acoustic wave on the surface of a liquid. Several devices are used to achieve this phenomenon. The oldest is the acoustic fountain in which the wave is oriented towards the free surface of a liquid at rest. If the acoustic intensity is sufficient, it forms an acoustic fountain whose conical shape focuses the ultrasonic wave. This fountain comes from the non-linearity of acoustic propagation which transforms a little vibratory energy into continuous energy (permanent flow) and forms a fountain that flows from the base upward. In this fountain the acoustic wave propagates and, as the section of the fountain is reduced, the acoustic concentration increases.

When the concentration is sufficient, the wall of the fountain vibrates strongly, it exceeds the cavitation threshold, which results in the creation of microdroplets on the walls of the jet. Only a part of the jet is nebulized, the rest of the fountain falls in large drops in the fluid. It is sufficient for an acoustic wave to have an intensity greater than the cavitation threshold so that the nebulization becomes possible.

The propagation conditions in the waveguides involve the notions of wave number with the relation: k _r ² + k _z ² = (w / C) ² with

- k _z wave number in the propagation axis in the jet,

- k _r wave number transverse to the axis of propagation in the jet,

- w = 2 ^* pi ^* f with f the frequency and

- C velocity in the fluid. It is realized that, depending on the fluids, the values of k _r and k _z are different since the celerities in the fluids vary, the boundary conditions on the walls of the jet (liquid / air interface) fixed with the value of the number k _r so that, depending on the diameter of the jet, there may be propagation of a wave or evanescent wave (the wave propagates if k _z is a real number).

The second known principle corresponds to the focusing on the free surface of the liquid to be sprayed with a parabolic reflector (French patent application FR9205306). The advantage over the previous technique is not to use the fountain to focus but a metal reflector (high impedance break). Thus, the acoustic wave is focused on the free surface of the liquid, the free surface and, as in the previous case, the horizontal free surface.

Thus, the acoustic fountain, which is formed, has a reduced base section (the concentration is higher at the base of the fountain) and, therefore, the cavitation threshold is easier to reach. With the same energy, the flow of nebulized liquid is five to six times higher than with the conventional acoustic fountain.

The third known principle is the nozzle (French patent application 94 08204). This third principle is very similar to the hard reflector principle, but in this case the focusing is carried out by the interior of a nozzle (the reflective surface is a paraboloid whose axis of rotation is the axis of propagation of the wave to concentrate, the focusing point being placed at the outlet of the nozzle).

Thanks to a pump, the liquid to be sprayed is propelled through this nozzle to create a jet. At the base of the nozzle, an acoustic wave of compression is sent by advancing in the nozzle the wave concentrates until the exit of the nozzle. In the free jet from this nozzle, the cavitation threshold is reached and a portion of the jet is nebulized.

Acoustic nebulization is strongly related to the phenomenon of cavitation. There are several types of cavitation: - the weak cavitation, when the variation of pressure necessary to obtain the cavitation is weak: it is the case of the fluids containing dissolved gases or micro-impurities and

- Strong cavitation, obtained when the fluid is perfectly degassed, in this case the minimum pressure variation is much stronger.

In the context of the present invention, only weak cavitation is mentioned. Indeed, liquids with a free surface always contain dissolved gases. When the fluid to be atomized contains dissolved gases, the acoustic wave allows the creation of gas microbubbles. If the frequency of the acoustic wave coincides with the resonance proper of the gas bubble, its diameter oscillates and becomes a source of nebulization. The nebulization rate depends on the acoustic power of the ultrasonic wave and the density of sites, called "germs", likely to give rise to a bubble.

The density of germs is very important in the fluid and the diameters of the bubbles generated are very variable.

The smaller the germs, the higher the frequency that excites them. It is therefore interesting to stimulate a maximum of germs to increase the flow of nebulization. To achieve this, it is sufficient for the propagating acoustic wave to have a spectral component rich in frequencies.

The performance of such devices is particularly low.

SUMMARY OF THE INVENTION

The present invention aims to remedy all or part of these disadvantages.

For this purpose, according to a first aspect, the present invention aims at a device for nebulizing a liquid comprising:

an open tank in its upper part and configured to contain the liquid to be sprayed,

at least two ultrasonic wave generators for emitting at least two ultrasonic wave fronts in the liquid, at least two means for focusing ultrasonic waves, each cooperating with a said generator for concentrating ultrasonic waves at the same point contributing to less than ten millimeters of the free surface of the liquid,

wherein the vibration frequencies of the two wavefronts are different.

Ultrasonic waves are understood to mean sound waves whose vibration frequency is greater than 20 kHz.

Thanks to these provisions, the nebulization device object of the invention makes it possible to focus two wave fronts at the same point close to the surface of the liquid. Since the surface of the liquid is in contact with air, gases are dissolved in the liquid, in particular in the form of microbubbles of gas, these microbubbles being cavitation nuclei. Thus, the device that is the subject of the invention makes it possible to subject the liquid to a low cavitation phenomenon, that is to say that if the frequency of the wavefront coincides with the resonance frequency of the gas micro-bubble, the diameter of the micro bubble varies, which creates the phenomenon of cavitation, and thus allows the nebulization of the liquid. The smaller the diameter of a bubble, the higher the frequency that makes the bubble vibrate.

The concurrent point is close to the free surface of the liquid. The term "close to the surface", less than ten millimeters, the free surface of the liquid, and preferably less than five millimeters, and even more preferably, less than three millimeters. ".

In addition, the frequencies f1 and f2 of the waves being close, the vibration field of the liquid at the concurrent point and the frequency spectrum between f1 and f2 is scanned. Thus, the number of cavitation nuclei reached, that is to say the gases dissolved in the liquid, is increased, which has the unexpected consequence of reducing the cavitation threshold of the liquid, and therefore of increasing the yield of the liquid. device object of the invention.

Indeed, a gas dissolved in the liquid is in the form of dissolved gas bubbles. The dimensions of the gas bubbles thus vary according to the vibrations to which they are subjected. In particular, dimensions of the dissolved gas bubbles impose a resonance vibration.

In particular embodiments, the means for focusing ultrasonic waves are nozzles configured to focus the ultrasonic waves at a point.

In particular embodiments, the means for focusing ultrasonic waves are ultrasonic wave reflectors, of the form impedance-breaking reflector type configured to focus the ultrasonic waves at a point.

In particular embodiments, the means for focusing ultrasonic waves are ultrasonic wave nozzles or reflectors of the form impedance-breaking reflector type configured to focus the ultrasonic waves at a point.

In particular embodiments, the means for focusing ultrasonic waves are cylindrical or parabolic impedance-breaking ultrasonic wave reflectors.

In particular embodiments, at least one means for focusing ultrasonic waves is a wall containing a gas or silica airgel type.

In particular embodiments, the vibration frequencies of the two wavefronts are greater than 1 MHz.

In particular embodiments, the vibration frequencies f1 and f2 of the two wavefronts are such that f1 is less than f2 and the ratio (f2 - f1) / (f1 + f2) is less than 5%.

In particular embodiments, the vibration frequencies f1 and f2 are such that f1 is less than f2 and the ratio (f2 - f1) / (f1 + f2) is less than 3%

In particular embodiments, the vibration frequencies f1 and f2 are such that f1 is less than f2 and the ratio (f2 - f1) / (f1 + f2) is less than 1%. In particular embodiments, the vibration frequencies f1 and f2 are such that f2-f1 is between 10 and 30 kHz, f1 being greater than 1.5 MHz.

Thanks to these arrangements, at the concurrent point, the frequencies of the wave fronts being close, an acoustic field of close frequencies is created, which therefore comprises the frequencies f2 - n ^* (f2-f1), n being an integer between 0 and f2 / (f2 - f1). The frequency spectrum is thus increased, as well as the number of cavitation nuclei reached.

Unexpectedly, the beat created by the proximity of the waves increases locally, that is to say that, at the concurrent point, the intensity of the wave fronts increases.

In particular embodiments, the ultrasonic wave generators are piezoelectric ceramics or activators.

In particular embodiments, the wave reflectors are at the same distance from the surface of the liquid.

In particular embodiments, the device according to the invention comprises a means for measuring the height of the liquid in the tank, the device comprising a means for supplying the tank in said liquid.

Thanks to these provisions, the competing point remains at a desired distance from the surface of the liquid.

In particular embodiments, the ultrasonic wave reflectors are configured to vary the position of the concurrent point.

In particular embodiments, the device according to the invention comprises a means for measuring the position of the concurrent point in the liquid, the ultrasonic wave reflectors being configured to vary the position of the concurrent point according to said measurement. .

In particular embodiments, the device which is the subject of the invention further comprises means for moving the nebulized liquid beyond the surface of the tank.

In particular embodiments, the device which is the subject of the invention further comprises an acoustically transparent membrane. and positioned on the wave generators to physically separate said generators and the liquid to be sprayed.

It should be noted that the membrane may, in addition, make it possible to control the operating temperature of the ultrasonic wave generator.

Thanks to these provisions, the liquid can not damage the wave generators.

In particular embodiments, the device which is the subject of the invention further comprises a nozzle placed in the liquid.

The nozzle advantageously makes it possible to set the acoustic propagation conditions in the jet, since it imposes a flow diameter of the liquid to be sprayed.

In particular embodiments, the liquid is a fuel of the alcohol, gas oil or gasoline type, or containing hydrocarbons, or chemical compounds comprising at least hydrogen, oxygen or carbon.

According to a second aspect, the present invention relates to a method of nebulizing a liquid contained in an open vessel in its upper part comprising:

a step of generating at least two ultrasonic wave fronts in the liquid using ultrasonic wave generators,

a step of focusing the wave fronts at the same point contributing to less than ten millimeters of the surface of the liquid,

wherein the vibration frequencies of the two wavefronts are different.

In particular embodiments, the method of nebulization object of the invention further comprises a step of moving the nebulized liquid out of the tank.

According to a third aspect, the present invention aims at a use of the device according to the invention for the nebulization of a liquid.

In particular embodiments, the use of the device that is the subject of the invention aims at humidifying the air. In particular embodiments, the use of the device that is the subject of the invention aims at cooling the air.

In particular embodiments, the liquid contains dissolved salts.

In particular embodiments, the use of the device which is the subject of the invention aims at obtaining drinking water.

In particular embodiments, the use of the device that is the subject of the invention aims at obtaining drinking water and recovering crystallized salts.

In particular embodiments, the use of the device which is the subject of the invention aims to obtain drinking water, the liquid to be sprayed being gray water or black water.

"Gray water" is understood to include water comprising pollutants, for example water of domestic origin, resulting from the washing of dishes, hands, baths or showers.

"Black water" is understood to include water containing various substances that are more polluting or more difficult to remove, such as faeces, cosmetics, or any type of industrial by-product mixed with water.

In particular embodiments, the use of the device which is the subject of the invention aims at the manufacture of powders by spraying liquid containing a crystallizable product, in a controlled atmosphere.

Thanks to these provisions, the nebulized drops evaporate and a crystal is formed. A calibrated powder is prepared, the size of the powder is likewise dispersed in diameter as the nebulized drops, that is to say that

98% of the particles have the same size)

In particular embodiments, the use of the device that is the subject of the invention aims to create a fog, the liquid having a high surface tension and a low vapor pressure.

In particular embodiments, the use of the device that is the subject of the invention is aimed at washing the polluting gases. In particular embodiments, the use of the device which is the subject of the invention aims at moistening fabrics for improving ironing.

In particular embodiments, the use of the device that is the subject of the invention aims at the creation of a mixture of fuel and oxidant.

Since the advantages, aims and particular characteristics of this method and of this use are similar to those of the device that is the subject of the present invention, they are not recalled here. BRIEF DESCRIPTION OF THE FIGURES

Other advantages, aims and features of the present invention will be understood from reading the following nonlimiting description, written with reference to the accompanying drawings, in which:

FIG. 1 represents, in perspective, a particular embodiment of the device that is the subject of the invention

FIG. 2 represents, in the form of a logic diagram, steps of a particular embodiment of the method that is the subject of the present invention.

DETAILED DESCRIPTION OF AN EMBODIMENT OF THE INVENTION

It will be recalled that, in the context of the present invention, only weak cavitation is mentioned. FIG. 1 shows a device 100 for nebulizing a liquid comprising a vessel 1 open in its upper part 1 12 and configured to contain the liquid to be sprayed. The device further comprises two ultrasonic wave generators 120, 130 for emitting two ultrasonic wave fronts 122 and 132, respectively, into the liquid, two means 124 respectively 134 for focusing ultrasonic waves, each cooperating with a said generator 120, respectively 130, for concentrating ultrasonic waves at the same point P competing close to the surface. By "close" is meant less than ten millimeters of the free surface of the liquid, and preferably less than five millimeters and even more preferably less than three millimeters.

The flow diagram of FIG. 2 represents a particular embodiment of the method for implementing the invention, which comprises:

a step 200 of generating at least two ultrasonic wave fronts 122 and 132 in the liquid using ultrasonic wave generators 120 and 130, and

a step 210 of focusing the wave fronts 122 and 132 at a same point P competing close to the surface of the liquid.

The liquid typically comprises water, or dissolved salts, or hydrocabures, or chemical or organic compounds comprising at least hydrogen, oxygen or carbon.

The tank 1 10 can also be filled with two non-missible liquids or separated into two liquid phases by a membrane 150, acoustically transparent.

Thus, a lower liquid phase 140 and an upper liquid phase 145 are designated, the lower liquid phase 140 being in contact with the wave generators 120 and 130, and the means 124 and 134 for focusing ultrasonic waves, and the liquid phase superior comprising the point of concurrence P.

Typically, the lower liquid phase 140 is, on the one hand, chosen so that it does not involve wear to the wave generators and, on the other hand, so as to be acoustically transparent. Thus the lower liquid phase 140 is a wave propagation medium.

For example, the lower liquid phase 140 is of the type of an incompressible gel and whose acoustic attenuation is less than 2 dB / cm.

Thus, the ultrasonic wave generators 120 and 130 are protected from the air by the lower liquid phase 140.

The focusing means 124 and 134 are typically ultrasonic impedance-breaking wave reflectors. We define the acoustic impedance of a body as the product of its density by the speed of sound in that body. Thus, the impedance break is a break in the continuity of the impedance of two bodies in contact.

Typically, the wave reflectors 124 and 134 are chosen so that their impedances are at least ten times greater than that of the liquid in which the wave reflectors 124 and 134 are immersed.

In addition, the wave reflectors 124 and 134 are typically of cylindrical or parabolic shape, so as to focus the wave fronts at the competing point P, close to the liquid surface.

In embodiments, at least one means 124 or 134 for focusing ultrasonic waves is a gas-containing wall or silica airgel.

In embodiments, the ultrasonic wave reflectors 124 and 134 are configured to vary the position of the concurrent point P. For example, these reflectors 124 and 134 are rotated by electric motors. Preferably, the device 100 for nebulizing a liquid comprises means for measuring the position of the concurrent point in the liquid, the ultrasonic wave reflectors 124 and 134 being configured to vary the position of the concurrent point according to said measurement. . In embodiments, the measurement of the position of the concurrent point P with respect to the liquid surface is a measure of the liquid height in the device 100. In embodiments, the measurement of the position of the point Concurrent with the surface of the liquid P is a measure of the quantity of nebulized liquid.

The ultrasonic wave generators 120 and 130 are typically power ceramics, of the lead titanozirconate type.

It is known to those skilled in the art that wave generators are piezoelectric ceramics or activators or single crystal activators.

Each of the two power ceramics 120 and 130 has its own resonance frequency, i.e. a physical quantity. representative of its behavior when the ceramic oscillates in free evolution.

Ceramics 120 and 130 of power are supplied by electrical circuits (not shown) so that their own resonance frequencies are typically between one MHz and three MHz. The electrical circuits are supplied with electricity by batteries (not shown) or by an electrical connection to the sector 121, respectively 131.

Typically, the frequencies f1 and f2 of the resonances of ceramics 120 and 130 are of the order of megahertz. In addition, the frequencies of the two wave fronts 122 and 132 are respectively those of ceramics 120 and 130.

The two ceramics are chosen, typically, so that their resonant frequencies f1 and f2 are very close to lowering the cavitation threshold.

Typically, ceramics of powers are chosen such that the frequencies f1 and f2 are different, f1 being less than f2 and the ratio (f2-f1) / (f1 + f2) being less than 5%. Preferably, ceramics of powers are chosen such that the ratio (f 2 - f 1) / (f 1 + f 2) is less than 3%. Advantageously, ceramics of powers are chosen such that the ratio (f 2 -f 1) / (f 1 + f 2) is less than 1%.

In embodiments, the vibration frequencies f1 and f2 are such that f2-f1 is between 10 and 30 kHz, for example 20 kHz, preferably between 20 kHz and 30 kHz, f1 being greater than 1.5 MHz.

The reflectors 124 and 134 may be of metal to have an impedance greater than that of the propagation liquid, or of very light material having a low celerity, for example a gas, so that more than 80% of the incident wave is thoughtful.

The shape of the reflectors is typically spherical or parabollic, so that the reflected waves are focused at the point P, common and concurrent of the two waves, and close to the surface of the liquid. Thus, when the two ceramics are excited, it is formed on the surface of the liquid, an acoustic fountain or jet and a cloud of goulettes on the surface of the jet.

The nebulized liquid flow rate is proportional to the pressure difference between the cavitation threshold and the wave pressure, the nebulized liquid flow rate is of the order of twice the reference flow rate, this reference flow being the Nebulizable flow by a single ceramic with its reflector.

The two ceramics being chosen so that their resonance frequencies f1 and f2 are very close, the nebulized flow is greater than the sum of the two reference flow rates.

As shown in Figure 1, the device comprises ceramics and reflectors at the same distance from the surface of the liquid.

In embodiments, the device 100 comprises an acoustically transparent membrane (not shown) positioned on the wave generators 120 and 130 for physically separating said generators and the liquid to be sprayed.

It is obvious to the person skilled in the art that, depending on the dimensions of the ceramics, the dimensions of the reflectors or the dimensions of the tank or the quantities of liquid to be sprayed, the device 100 may comprise more generators and reflectors. The generators 120 and 130 and the reflectors 124 and 134 may be placed at the same distance from the surface of the liquid or placed at different distances from the surface of the liquid. In addition, the device 100 may also include more points near the surface, in which waves are focused. Likewise, more different frequencies can be implemented.

As shown in FIG. 1, the device 100 may comprise a nozzle 160 placed between the concurrent point P and the wave generators 120 and 130.

In addition, the device 100 may comprise a means 170 for measuring the height of the liquid in the vessel 1 10 and a means (not shown) for supplying the tank with liquid. This nozzle 160 is typically made of metal when the liquid is water, a diameter of the nozzle is between two mm and ten mm.

By fixing this diameter, the initial jet velocity as well as the length of the jet are fixed because the nozzle 160 imposes propagation conditions of the ultrasonic wave fronts in the jet. The nozzle 160 makes it possible to adapt the nebulizing device 100 to liquids that are difficult to nebulize (according to the explanation given in the state of the art), in particular the fluids with high surface tension and low vapor pressure.

The device 100 described is particularly suitable for the nebulization of various liquids. This nebulization aims to:

- spray these products, if they are vaporizable

- humidify or cool the air, especially the dechambering of a passenger compartment of a vehicle,

- accelerate the rate of change of state (liquid / vapor) of the nebulized liquid,

deodorizing or perfuming air by nebulising a perfume or an active ingredient dissolved in the liquid,

- prepare saturated gases,

preparing for the combustion of vapor of combustible product and in particular nebulizing a fuel of the alcohol, gas oil or gasoline type, or containing hydrocarbons, or chemical compounds comprising at least hydrogen, oxygen or carbon,

- If the fluid is a solution of dissolved salts, the device is particularly suitable for the separation of salts and their solvent.

The targeted applications are:

desalination of seawater for recovery of fresh water and solid salts, the liquid containing dissolved salts,

- the treatment of wastewater, particularly "black water" or "gray water" to obtain drinking water,

- the manufacture of calibrated fine powder,

- the humidification of the air,

- the cooling of the air, - obtaining drinking water,

the recovery of crystallized salts,

- Obtaining drinking water, the liquid to be sprayed is gray water or black water,

the manufacture of powders by spraying liquid containing a crystallizable product, in a controlled atmosphere,

the creation of a mist, the liquid preferably being of high surface tension and low vapor pressure,

- the washing of the polluting gases,

- the humidification of fabrics for improving ironing and / or

- the creation of fuel and oxidant mixture.

Claims

1. Device (100) for nebulizing a liquid characterized in that it comprises:

- a tank (1 10) open in its upper part and configured to contain the liquid to be sprayed,

at least two ultrasonic wave generators (120, 130) for emitting at least two edges (122, 132) of ultrasonic waves into the liquid,

at least two means (134, 124) for focusing ultrasonic waves, each cooperating with a said generator (120, 130) for concentrating ultrasonic waves at the same point (P) within ten millimeters of the free surface of the liquid ,

in which the vibration frequencies of the two wave fronts (122, 132) are different.

The liquid nebulizing device (100) of claim 1, wherein the means (124, 134) for focusing ultrasonic waves are nozzles configured to focus the ultrasonic waves at a point.

3. Device (100) for nebulizing a liquid according to claim 1, wherein the means (124, 134) for focusing ultrasonic waves are ultrasonic wave reflectors, type impedance reflectors of configured shapes to focus the ultrasound waves at one point.

4. Device (100) for nebulizing a liquid according to one of claims 1 or 3, wherein the means (124, 134) for focusing ultrasonic waves are ultrasonic wave reflectors with impedance breaking form cylindrical or parabolic.

5. Device (100) for nebulizing a liquid according to one of claims 1 to 4, wherein at least one means (124, 134) for focusing ultrasonic waves is a wall containing a gas or silica airgel type .

6. Device (100) for nebulizing a liquid according to one of claims 1 to 5, wherein the vibration frequencies of the two wave fronts (122, 132) are greater than 1 MHz.

7. Device (100) for nebulizing a liquid according to one of claims 1 to 6, wherein the vibration frequencies f1 and f2 of the two wavefronts (122, 132) are different, f1 being less than f2 and the ratio (f2 - f 1) / (f 1 + f2) being less than 5%.

8. Device (100) for nebulizing a liquid according to one of claims 1 to 7, wherein the vibration frequencies f1 and f2 of the two wavefronts (122, 132) are different, f1 being less than f2 and the ratio (f 2 - f 1) / (f 1 + f 2) being less than 3%.

9. Device (100) for nebulizing a liquid according to one of claims 1 to 8, wherein the vibration frequencies f1 and f2 of the two wavefronts (122, 132) are different, f1 being less than f2 and the ratio (f 2 - f 1) / (f 1 + f 2) being less than 1%.

10. Device (100) for nebulizing a liquid according to one of claims 1 to 9, wherein the vibration frequencies f1 and f2 are such that f2 - f 1 is between 10 and 30 kHz, f1 being greater than 1 , 5MHz.

1 1. Device (100) for nebulizing a liquid according to one of claims 1 to 10, wherein the generators (120, 130) of ultrasonic waves are ceramics or piezoelectric activators.

12. Device (100) for nebulizing a liquid according to one of claims 1 to 1 1, wherein the wave reflectors (124, 134) are at the same distance from the surface of the liquid.

13. Device (100) for nebulizing a liquid according to one of claims 1 to 12, which comprises a means for measuring the height of the liquid in the tank, the device comprising a feed means of the tank in said liquid.

14. Device (100) for nebulizing a liquid according to one of claims 1 to 13, wherein the ultrasonic wave reflectors are configured to vary the position of the concurrent point.

15. Device (100) for nebulizing a liquid according to one of claims 1 to 14, which comprises a means for measuring the position of the concurrent point in the liquid, the ultrasonic wave reflectors being configured to vary the position of the competing point according to said measurement.

16. Device (100) for nebulizing a liquid according to one of claims 1 to 15, which comprises an acoustically transparent membrane and positioned on the wave generators for physically separating said generators and the liquid to be sprayed.

17. Device (100) for nebulizing a liquid according to one of claims 1 to 16, which comprises a nozzle placed in the liquid.

18. Device (100) for nebulizing a liquid according to one of claims 1 to 17, wherein the liquid is a fuel type alcohol, gas oil or gasoline, or containing hydrocarbons, or chemical compounds comprising at least hydrogen, oxygen or carbon.

19. A method of nebulizing a liquid contained in an open vessel in its upper part comprising:

a step (200) of generating at least two ultrasonic wave fronts in the liquid using ultrasonic wave generators, a step (210) of focusing the wave fronts at the same point competing at least ten millimeters from the surface of the liquid,

wherein the vibration frequencies of the two wavefronts (122, 132) are different.

20. The method of claim 19, which comprises a step of moving the nebulized liquid out of the tank.

21. Use of the device according to one of claims 1 to 18 for the nebulization of a liquid.

22. Use according to claim 21 for humidifying air.

23. Use according to claim 21 for cooling air.

24. Use according to claim 21 for obtaining drinking water.

25. Use according to claim 21 for recovering crystallized salts.

26. Use according to claim 21, for obtaining drinking water, the liquid to be sprayed is gray water or black water.

27. Use according to claim 21, for the manufacture of powders by spraying liquid containing a crystallizable product, in a controlled atmosphere.

28. Use according to claim 21, for the creation of a fog, the liquid being of high surface tension and low vapor pressure.

29. Use according to claim 21, for washing polluting gases.

30. Use according to claim 21, for the humidification of fabrics for improving ironing.

31. Use according to claim 21 for the creation of fuel and oxidant mixture.