WO1999008783A1 - Method and device for preparing an emulsion from immiscible constituents - Google Patents

Abstract

The invention concerns a method for preparing an emulsion from immiscible constituents comprising at least a liquid by treating them with a first periodic action (3), producing a cavitation effect, characterised in that it consists in: introducing in the treatment process the immiscible constituents (2), at least a supplementary periodic action (4) whereof the frequency differs from the frequency of the first periodic action by at least a factor 10; forming in the liquid medium acoustic resonators constituted by bubbles of gas, vapour or their combinations, and constituting part of the immiscible constituents, by introducing gas, vapour or their combinations (8); modulating by the supplementary periodic action (4), said first periodic action (3) with a frequency, phase and/or amplitude modulation, or a combined modulation; acting by resonance using the spectral components formed by the modulation, on the immiscible constituents (2) whereof the particular frequencies are equal and/or correspond on the whole to the frequencies of said spectral components, thereby producing a cavitation phenomenon which breaks down the particles of the immiscible constituents and brings about the formation of a stable, homogeneous and fine emulsion.

Description

 Process and device for preparing an emulsion from immiscible constituents.

The present invention relates to a process for preparing an emulsion from immiscible constituents of liquid and gaseous and / or solid media by treatment of these constituents by means of periodic external actions as well as a device for the implementation of this process .

The state of the art relating to the present invention is a method and a device for preparing an emulsion based on the production of a cavitation effect in a mechanical and / or acoustic treatment process for liquid, gaseous and / or solid.

For the determination of the ^fundamental drawbacks of the conventional method of obtaining the cavitation effect with a view to the preparation of emulsions, we will examine the physical nature of the mechanism of appearance of cavitation under the effect of ultrasound. called "ultrasonic cavitation".

The ultrasonic cavitation effect is as follows. The ultrasonic oscillations generate in the liquid areas of high and low pressures alternating according to their frequency.

In a discharged area, the hydrostatic pressure decreases to the point that the separation forces acting on the particles of the liquid become greater than the bonding forces between the particles.

As a result of the sudden modification of the hydrostatic equilibrium, during the alternation of extension, the liquid is subjected to a sort of bursting, generating numerous bubbles of very small dimensions of gas and vapor, which are previously found , that is to say before the ultrasonic action, in the dissolved state in the liquid. These bubbles are called "cavitation germs". At the following moments, during the alternation of compression, thanks to the high pressures, the gas bubbles which have previously formed, snap that is to say burst. The shock waves with a very high local instantaneous pressure reaching several hundreds of atmospheres which appear then divide the constituents not miscible, mix them, causing an emulsion to form.

Ultrasonic cavitation in a liquid depends on its density, viscosity, temperature, molecular mass, compressibility, gas content, presence of microscopic inclusions, frequency and intensity ultrasound, static pressure, and a host of other facts and their combinations.

Using the combined interaction of these facts, characteristics and parameters, we ultimately determine the cavitation effect which can be represented by two global characteristics:

- presence of the cavitation germ formation process; - quantity of cavitation germs.

These characteristics do not lend themselves to calculation and it is not possible to obtain their knowledge and information by experimental means.

However, experience has certainly shown that the efficiency of cavitation increases with increasing power, but decreases with increasing frequency of ultrasound. It is also established that the formation of cavitation germs can begin for low intensities of ultrasound. In this way, the contemporary scientific explanation of the mechanism of ultrasonic cavitation is linked with a classic representation of the actions of forces on immiscible liquid and gaseous media, ultimately causing the compression of cavitation germs. The frequency of ultrasound (in general the frequency of periodic action) has no direct relationship with the process of breakdown and bursting of gas bubbles, it conditions the efficiency of cavitation, but the law of their binding is unknown. It follows from the foregoing analysis that the main drawbacks of existing methods for preparing emulsions based on the classic cavitation effect are a high energy consumption, the complexity of the calculation parameters of the process and its optimization, low efficiency and the need to use various types of emulsifiers: chemical bodies with surface activity for the stabilization of lesions. The object of the invention is to remedy the aforementioned drawbacks and to increase the functional possibilities of the method and the device.

To this end, the subject of the invention is a process for the preparation of emulsions from immiscible constituents comprising at least one liquid by means of their treatment with at least a first periodic action, producing a cavitation effect, characterized in that that the immiscible constituents are introduced into the treatment process, at least one additional periodic action whose frequency differs from the frequency of the first periodic action by at least a factor of 10, acoustic resonators formed are formed in the liquid medium by gas bubbles, vapor or combinations thereof, and which constitute a part of the immiscible constituents, by introduction of gas, vapor or their combinations, said first action is modulated by means of the additional periodic action periodic by frequency, phase and / or amplitude modulation, or by combined modulation, we act by resonance using the spectral poses which are formed due to the modulation, on the immiscible constituents whose natural frequencies are equal and / or correspond on the whole to the frequencies of the aforementioned spectral components and one thus realizes a phenomenon of resonant cavitation which causes the rupture particles of the immiscible constituents and the formation of a stable, homogeneous and fine emulsion.

According to another characteristic of the invention, the process for treating immiscible constituents is optimized by means of adaptive combinatorial regulation of the parameters of the first and second periodic actions such as the amplitudes, the phases and / or the frequencies.

The invention will be better understood on reading the description which follows, given only to as an example and made with reference to the accompanying drawings in which:

- Fig.l shows the block diagram of a device implementing the new method of making resonance emulsions; FIG. 2 is a diagram of another embodiment of the device for producing emulsions according to the invention; - Fig.3 is a diagram of a variant of the device of Fig.2;

- Fig.4 is a diagram of another variant of the device of Figs.2 and 3;

- Fig.5 is a diagram of an electromechanical embodiment of the device of the invention; and Fig.6 is a diagram of a variant of the device of Fig.3.

The device represented in FIG. 1 comprises a reservoir 1 containing immiscible constituents 2 formed from liquid and gaseous media, for example, one or more petroleum products, water and air, at least a first source of periodic action 3, for example an ultrasonic exciter, associated with a generator 3a, placed in the tank 1, at least one second source of periodic action 4 placed in the tank 1 opposite the first source of periodic action 3 , for example a mechanical, acoustic or magnetostrictive vibrator associated with a generator 4a, the frequency of which is at least 10 times lower than the frequency of the first source 3, a regulating device 5, automatically and adaptively modifying the parameters of the first and second sources of periodic action such as amplitudes, phases and / or frequencies for example, an automatic regulation system optimizing the p repair of emulsions with regard to energy expenditure and emulsification rates.

The liquid and gaseous media and the solid material are introduced into the tank 1 through pipes 7,8,9 respectively and the emulsion obtained is evacuated through a conduit 10.

The regulation system 5 comprises for example sensors for parameters of the sources of periodic action and a servo system between the first and second sources of periodic action (not shown).

The first and second energy sources 3 and 4 of periodic actions as well as the regulating device 5 are not shown in detail in FIG. 1. In FIG. 2, a block diagram of a similar device is shown. to that of figure 1.

Unlike the arrangement of FIG. 1, in the device of FIG. 2, the second periodic action means is constituted by a passive oscillating system, for example a mechanical vibrator 14 comprising at least one parabolic reflector 14a mounted in the tank 11 by means of a spring 14b. The natural frequency of such a vibrator is determined by its mass and by the elastic modulus of the spring 14b. The oscillations of the vibrator 14 at its natural frequency during the operation of the device of Figure 2 can be excited for example due to the action on it of currents of liquid media and / or gaseous media generated in the medium formed immiscible constituents 12 by the first periodic means of action 13 comprising an ultrasonic exciter associated with a generator 13a on the constituents 12 contained in the reservoir 11. The gaseous liquid media and a solid matter in particles are introduced into the container 11 by conduits 17, 18 and 19 and the emulsion obtained is evacuated by a conduit 20. The parabolic reflector can also be associated with an electromagnetic drive device.

In Figure 3, there is shown a block diagram of a device similar to that of Figure 1 and which differs from it in that the second periodic action means 24 is formed of a passive oscillating system by example a mechanical vibrator is linked by active direct coupling for example an electromechanical or acoustic vibrator of the first periodic action means 23 associated with a generator 23a.

The operating principle of the system 24 is analogous to that of the device 14 of FIG. 2. The action of the means 13 on the means 14 is not limited by the configuration of the diagram shown in FIG. 2.

The second periodic action source 24 can ensure its action on the first source 23 by direct coupling, as shown in FIG. 3. In this case, these are the multiple frequency modulated oscillations emitted by the two sources 23,24 combined which act on the medium 22 formed of immiscible constituents.

The second source 24 of periodic action can also act on the power source using a command and control system 25 or by these two combined means.

Such a variant of mutual action is represented in FIG. 4 in which a first periodic action means 33 and more particularly its generator 33a is modulated by a second periodic action means 34 for example a frequency modulator, at the using a regulatory system 35.

It therefore delivers modulated oscillations which propagate in the immiscible constituents 32 and cause the formation of the emulsion. Here again, the liquid, gaseous and solid constituents are introduced into the container 31 through conduits 32, 38 and 39 and the emulsion is discharged through a conduit 40.

In Figure 5, there is shown a block diagram of a device similar to that of Figure 1 and which differs therefrom in that the first periodic action means comprises an acoustic emitter 43 produced in the form of '' a siren or a whistle, while the second periodic means of action is produced in the form of a passive oscillating system 44 such as a mechanical vibrator whose operating mode is analogous to the operation of the device 14 of the figure 2.

The acoustic transmitter 43 can be produced for example in the form of a system in the construction of which between an electromechanical device such as a rotor 43a driven in rotation by an electric motor 43b and at least one stator 43c provided with perforations and mounted so as to be able to vibrate in a support 46 by means of springs 44 which precisely form the system oscillating passive.

The rotor 43a and the stator 43c form the acoustic emitter of the liquid siren type. The rotor 43a is immersed in the immiscible constituents 42 contained in a reservoir 41, one wall of which is formed by the support 46 of the springs 44 which form the second means of periodic action.

The immiscible constituents such as a fuel, water and air are introduced into the container 42 by conduits 47, 48 and 49 while the emulsion obtained is evacuated by an evacuation orifice 50.

The evacuation orifice comprises a tube possibly provided with a sprayer (not shown).

It is also possible to envisage using an arrangement in which the additional periodic action source comprises at least one membrane and an electromagnetic device for driving the latter.

The device shown in FIG. 6 comprises a reservoir 51 containing the immiscible constituents 52 from which the emulsion must be produced.

In this device, the additional periodic action means is, unlike the arrangement of FIG. 3, formed by an active oscillating system such as an electromechanical or acoustic vibrator 54 and its associated generator 54a, directly coupled to the first means d periodic action 53 constituted by a mechanical vibrator and its associated generator 53a.

The vibrators 53 and 54 are controlled by a regulation system 55 according to the operating regime to be obtained.

Reservoir 51 is associated with conduits 57, 58, 59 for admitting liquid, gaseous constituents and particulate solid materials, as well as a conduit 60 for discharging 1 emulsion obtained.

All these conduits, like those of the other embodiments of the device of the invention, are provided with flow control valves. The process according to the invention for preparing emulsions using the device, the diagram of which is shown in FIG. 1, is carried out as follows.

The first source 3 of periodic action acts on the medium 2 formed of the immiscible constituents contained in the reservoir 1 and creates the initial conditions for the preparation of the emulsion: appearance of acoustic waves of frequency F in the liquid medium of the constituents 2, appearance of mechanical movements and microcurrents in the medium 2, conditioned by the classic effect of acoustic cavitation.

The second periodic action source 4 acts on the medium 2 simultaneously with the first source 3 and causes the appearance in the medium 2 of low frequency oscillations f.

As a result of the interaction of the oscillations of different frequencies F and f, there is a modulation of the oscillations of high frequency F by the low frequency f, for example according to the frequency in accordance with known laws:

Ff, F + f, F-2f, F + 2f, ..., F-Nf, F + Nf, ..., (N = 0, 1, 2, 3, ...) and so in the middle 2 appears a spectrum of N frequency oscillations f _N.

The presence of the spectrum of oscillations of frequencies f _N brings to resonance excitation the immiscible constituents of the medium 2, for example the gas bubbles whose natural frequencies f _N are equal to the frequencies f _N of the frequency spectrum indicated more high.

From the theory of sound, it is known that bubbles of gas, for example air in a liquid constitute acoustic resonators or Helmoltz resonators (Rayleigh, Theory of Sound, London, 1986). For small gas bubbles, their resonant frequencies are determined by the relation f _N = 326 / R _N where R _N are the radii of the gas bubbles.

Thus, the process for the preparation of emulsions according to the invention makes it possible to ensure excitation by resonance simultaneously of a large number of acoustic resonators of gas bubbles of different diameters.

Such a process is analogous to an acoustic cavitation process but at the same time, it is radically different from it. It can be called "resonant cavitation effect".

To increase the efficiency of the preparation of the emulsions, the device 5 ensures, using appropriate sensors (not shown), an automatic tuning or modification of the radiation and modulation frequencies in conjunction with the variation of the temperature of the treated medium, its viscosity and other characteristics.

Thus, the ultrasonic action 3 on the immiscible constituents 2 resulting from the start of the conventional cavitation process creates the initial conditions for the realization of resonant cavitation.

After the application of the second periodic action 4, ensuring a modulation for example of frequency, of the first action 3, in the medium 2 formed of immiscible constituents, appear oscillations in a large frequency spectrum, which creates conditions participation in the resonant cavitation process of large numbers of gas bubbles of different diameters and eigenfrequencies which correspond to them forming as many gas resonators

Under these conditions, the resulting cavitation process increases in avalanche due to the sudden increase in the number of bursts of the particles forming resonators. The bursting of the resonators causes the particles of solid, liquid or gaseous media 2 which surround them to be fractionated and the constantly increasing quantities of resonator particles having natural frequencies to be entrained in the resonant cavitation process. different. As a result of resonant cavitation, a rapid and efficient fractionation of particles of solid, liquid and gaseous media takes place until an extremely fine state of dispersion, their mixing and the formation thanks to that of extremely stable emulsions, which not fall apart for tens and hundreds of days.

The resonant cavitation process can be considerably accentuated if the gas, for example the air entering into the composition of the immiscible constituents 2, is introduced in the form of small bubbles.

The operations of the devices described with reference to Figures 2 to 5 are similar to that of the device of Figure 1 and will therefore not be described.

In a specially created installation comprising the device of FIG. 1 and a series of control and measuring apparatuses, the process of preparing emulsions of the "water - air - petroleum products" type has been studied.

The tank 1 for studying the emulsion preparation process constituted an acoustic chamber whose plan dimensions were 50 x 100 mm and whose height was 100 mm.

In the tank 1, immiscible components 2 are introduced, for example fuel oil, water and air.

The acoustic action 3 is applied to the tank 1 by means, for example, of a piezoelectric or ceramic emitter. On the opposite side in the tank 1 is introduced a low frequency action 4 using for example a magnetostrictive or acoustic radiator.

The regulation system 5 makes it possible to modify the parameters of the periodic radiators such as the amplitudes, the frequencies and the phases.

The frequency of the ultrasonic action varied between 20 and 44 KHz.

The frequency of the action at low frequency underwent variations between 1 and 2000 Hz. The intensity of the ultrasound underwent variations between 1 and 25 W / cm ² .

The intensity of the low-voltage radiation underwent variations within the same limits. The experiments were carried out in the following manner.

First, the action efficiency of each of the periodic actions was examined separately for one minute. Experiments have shown that in an ultrasonic field of action with a frequency of 22 KHz for example, within intensity limits of 5 to 25 W / cm ² , there is cavitation. However, the emulsion obtained is not stable and completely breaks down after a few hours. Under the action of low frequency radiation, alone, within the same intensity limits, the cavitation process does not occur at all.

During a simultaneous action on the aforementioned constituents 2, exerted by the two periodic actions 3 and 4, the following results are obtained:

- for an intensity of the periodic action 3 within the limits of 5 to 10 W / cm ² and a frequency of 22 Khz and for an intensity of the periodic action at low frequency 4 within the limits of 3 to 5 W / cm ² and a frequency of 10 Hz for 10 s, a highly dispersed homogeneous emulsion was prepared, which retained its stability for more than 50 days.

The following indicators were obtained relating to the efficiency and the intensification of the process for preparing emulsions which produces a new resonant cavitation effect according to the invention:

reduction of the time necessary for the treatment of immiscible constituents 2 under the action of at least two radiators whose frequencies differ from 5 to 10 times;

- overall energy expenditure at least 7 to 10 times less than in conventional schemes for preparing emulsions;

- stability of the emulsion over time increased by at least 10 to 12 times.

The emulsion prepared by the resonant cavitation process according to the invention was tested in an individual boiler burner.

This emulsion, which can contain up to 50% water and only 50% domestic heating oil, makes it possible to obtain amounts of heat practically equal to the heat that can be obtained if 100% domestic fuel oil is used in the absence of water.

Similar results have been obtained when using a “diesel-water” type emulsion and

"gasoline-water" in internal combustion engines with a proportion of 65% diesel and 35% water for diesel engines and 60% gasoline and 40% water for gasoline engines.

Tests carried out on three installations specially created for this purpose have demonstrated: an energy saving of 20 to 40% for different percentages of water in the fuel and a reduction of the excitation time to 3 to 7 s without requiring chemical softening agent; - the almost total absence in the exhaust gases of toxic components of the NOx and C0 _{2 groups as} well as polluting components such as unburnt hydrocarbons; a significant reduction in the sound level of operation of the installations (fuel engines, burners, etc.).

Unlike traditional techniques, the solutions and structures offered allow serious savings in terms of energy consumption and an increase in the longevity of the installations. The invention can be applied to prepare a stable emulsion both from separate immiscible constituents and from such constituents already found in an emulsion obtained by a conventional process and therefore having insufficient homogeneity and stability as the process of the invention makes it possible to improve to the point of making the emulsion industrially usable.

The invention which has just been described applies to the production of emulsions from immiscible, liquid, solid, gaseous constituents or from combinations of such constituents.

These constituents can be in the form of molecules or sets of molecules.

The common characteristic of all the constituents likely to be part of an emulsion regardless of their physical nature is that they have oscillatory properties.

In other words, the various constituents or else their combinations must form potential oscillatory systems, that is to say systems capable under certain conditions of carrying out periodic movements.

The invention can be used for the preparation of emulsions intended for preparing paints, lacquers and varnishes, in oil, in water, based on pigments in powder or paste, glues and others.

The invention is also applicable for the production of emulsions intended for mechanical work, of hard materials, by cutting, drilling, polishing and others.

It is moreover applicable for the production of emulsions intended for the perfumery, the pharmaceutical industry, the food industry.

Finally, it is applicable to all cases in which it is necessary to produce or obtain emulsions or in which an emulsion is already used and produced.

Claims

1. Process for the preparation of emulsions from immiscible constituents comprising at least one liquid by means of their treatment with at least one first periodic action (3; 13; 23; 33; 3; 53), producing a cavitation effect , characterized in that the immiscible constituents (2; 12; 22; 32; 42; 52) are introduced into the treatment process, at least one additional periodic action (4; 14; 24; 34; 44; 54) whose frequency differs from the frequency of the first periodic action by at least a factor of 10, acoustic resonators formed by gas or vapor bubbles or their combinations are formed in the liquid medium and which constitute a part of the non-constituents miscible, by introduction of gas, vapor or their combinations (8; 18; 28; 38; 48; 58), one modulates with the aid of the additional periodic action (4; 14; 24; 34; 44; 54), said first periodic action (3; 13; 23; 33; 43; 53) by frequency modulation, of phas e and / or amplitude, or by a combined modulation, one acts by resonance with the help of the spectral components which are formed as a result of the modulation, on the immiscible constituents (2; 12; 22; 32; 42; 52) whose natural frequencies are equal and / or generally correspond to the frequencies of the aforementioned spectral components and a resonant cavitation phenomenon is thus produced which causes the particles of the immiscible constituents to rupture and the formation of a homogeneous stable emulsion and fine. 2. Method according to claim 1, characterized in that the treatment of immiscible constituents is optimized by a combined regulation (5; 15; 25; 35; 45; 55) of parameters of the first periodic action and of the action additional periodic, such as frequencies, phases and / or amplitudes. 3. Method according to one of claims 1 and 2, characterized in that the efficiency of the resonant cavitation process is increased by the introduction of gas, vapor and / or their combination (8; 18; 28; 38; 48; 58) in the composition of the immiscible constituents in the form of small bubbles, with their simultaneous acoustic excitation by passage of the gas-vapor constituents in at least one siren and / or whistle. 4. Method according to one of claims 1 to 3, characterized in that the frequency of the first periodic action is an ultrasonic frequency while the frequency of the additional periodic action is a low frequency. 5. Method according to one of claims 1 to 4, characterized in that the modulation of the oscillations of the first periodic action by the oscillatins of the additional periodic action is ensured within the immiscible constituents. 6. Method according to one of claims 1 to 4, characterized in that the modulation of the oscillations of the first periodic action by the oscillations of the additional periodic action is ensured by external coupling to the medium formed by the immiscible constituents. 7. Method according to one of claims 1 to 6, characterized in that the immiscible constituents comprise at least one solid in particles. 8. Method according to one of claims 1 to 6, characterized in that the immiscible constituents comprise a fuel and water. 9. Method according to one of claims 1 to 6, characterized in that the immiscible constituents comprise a solvent and at least one coloring powder material. 10. Method according to one of claims 1 to 6, characterized in that the immiscible constituents comprise a solvent and at least one powdered adhesive product. 11. Device for preparing emulsions from immiscible constituents intended for the implementation of the method according to one of claims 1 to 10, comprising a reservoir (1; 11; 21; 31; 41; 51) with immiscible constituents (2; 21; 22; 32; 42; 52) comprising at least one liquid, contained therein, at least one first source (3; 13; 23,24,25) of periodic action on these constituents, characterized in that it comprises means (8; 18; 28; 38; 48; 58) for the introduction of gas, vapor or from their combinations, at least one additional source (4; 14; 24; 34; 44; 54) of periodic action whose frequency differs from the frequency of the first source of periodic action by at least a factor of 10, and which constitutes a device for modulating the first periodic action according to a frequency, phase and / or amplitude modulation and for obtaining spectral components at multiple frequencies acting by resonant cavitation on the acoustic resonators constituted by gas bubbles, vapor or combinations thereof, and on the particles of the immiscible constituents for the formation of a stable emulsion. 12. Device according to claim 11, characterized in that it further comprises a system (5; 15; 25; 35; 45; 55) for regulating the parameters of the first source of periodic action and of the source of additional periodic action, which constitutes an automatic regulation system modifying the amplitudes, phases and / or frequencies of the aforementioned periodic action sources in correspondence with the variation of the conditions and characteristics of the emulsion preparation processes. 13. Device according to one of claims 11 and 12, characterized in that the additional periodic action source (24; 34; 54) is connected to the first periodic action source (23; 33; 53) by coupling outside the medium formed by immiscible constituents and directly modulates the latter to apply to the medium (22; 32; 52) formed of immiscible constituents the spectral components at multiple frequencies resulting from said modulation. 14. Device according to claim 13, characterized in that the coupling between the additional periodic action source (24; 54) and the first periodic action source (23; 53) is a direct coupling. 15. Device according to claim 13, characterized in that the coupling between the periodic action additional (34) and the first periodic action (33) is carried out via the regulation system (35). 16. Device according to one of claims 11 and 12, characterized in that the additional periodic action source (4; 14; 44) is connected to the first periodic action source (3; 13; 43) by the medium (2; 12; 42) formed from immiscible constituents, and in that the multiple frequency spectral components are formed by modulation in said medium. 17. Device according to one of claims 13 to 16, characterized in that the additional source of periodic action (4; 54) is formed by at least one active system comprising an oscillating system and an excitation means (4a; 54a) of the system oscillating at its natural frequency. 18. Device according to claim 16, characterized in that the additional periodic action source comprises at least one electromechanical vibrator comprising at least one parabolic reflector and an electromagnetic device for driving said reflector according to a periodic movement. 19. Device according to claims 16 and 17, characterized in that the additional periodic action source comprises at least one acoustic vibrator, comprising at least one membrane and an electromagnetic drive device for the latter. 20. Device according to one of claims 13 to 16 and claim 19, characterized in that the additional periodic action source comprises at least one modulator (34; 54) of frequency and / or phase acting on the first source periodic action (33; 53). 21. Device according to one of claims 13 to 16, characterized in that the additional source of periodic action (14) is formed of at least one passive system (14a) comprising at least one potentially oscillating system, capable of oscillate at its natural frequency under the action of an external excitation source and ensure the modulation of the periodic action of the first periodic action source (13). 22. Device according to claim 21, characterized in that the external excitation source of the additional periodic action source is the first periodic action source (13). 23. Device according to one of claims 21 and 22, characterized in that the additional periodic action source comprises at least one mechanical vibrator comprising at least one parabolic reflector (14a) arranged opposite the first periodic action source (13) and elastic means (14b) for support thereof, the natural frequency of said vibrator being determined by its mass and the modulus of elasticity of the elastic support means (14b). 24. Device according to one of claims 21 to 23, characterized in that the first periodic action source comprises an electromechanical system in the form of a liquid siren comprising a rotor (43a) driven in rotation by an electric motor (43b) and at least one stator (43c) provided with orifices, while the additional periodic action source (44) comprises a mechanical vibrator formed by said stator (43c) and connected to the reservoir (41) by at least one spring (44a).