IT201900014055A1 - DEVICE FOR THE EMISSION OF ACOUSTIC PULSES. - Google Patents

Description

DEVICE FOR THE EMISSION OF ACOUSTIC PULSES

DESCRIPTION

The present invention refers to a device for the emission of acoustic pulses particularly suitable for use in ecometric equipment, for example in ecometric equipment for underwater and inland water exploration.

As is known, an ecometric apparatus for submarine and inland water exploration generally comprises a device capable of generating acoustic pulses that propagate in the water until they hit the submarine soil, penetrating the layers up to varying depths according to their permeability and the characteristics of the signal. acoustic.

In this way, it is possible to obtain an “acoustic mapping” of the submarine soil which allows to study its composition and structure, for example also in order to identify any buried hydrocarbon deposits.

Devices for the emission of acoustic pulses, commonly referred to as the "sparker" type, have been known for some time, which include one or more pairs of electrodes intended to be immersed in water and electrically connected to a source of electrical power.

In the use of these devices, the source of electrical power supplies electrical energy to the above electrodes in such a way as to induce an electric discharge between the latter and the consequent transformation into the plasma state (a so-called "plasma bubble") of water in correspondence to a volume in the vicinity of the aforesaid electrodes.

The formation and subsequent sudden collapse or implosion of this "plasma bubble" generate an impulsive acoustic wave that propagates in the water to reach the underwater soil and be reflected or refracted by the latter's layers.

The devices of the "sparker" type, currently available, do not allow satisfactory control of the waveform (duration and pulse width) and the direction of propagation of the acoustic pulses emitted. This is reflected in a relatively low quality (for example with vertical resolution values much higher than 1 m) of the “acoustic images” of the underwater soil that can be obtained thanks to the reflection and reception of the transmitted acoustic impulses. The main task of the present invention is to provide a device for the emission of acoustic pulses for ecometric apparatuses that allows to overcome the drawbacks of the prior art, highlighted above.

As part of this task, an object of the present invention is to provide a device for the emission of acoustic pulses capable of emitting acoustic pulses of high quality in terms of duration and amplitude.

A further purpose of the invention is to provide a device for the emission of acoustic pulses capable of emitting acoustic pulses having an easily controllable direction of propagation.

A further purpose of the invention is to provide a device for emitting acoustic pulses with high power, for example in the order of tens of KJ.

A further purpose of the invention is to provide a device for the emission of acoustic pulses that is relatively simple to install in the field and easy to use in practice.

A further object of the present invention is to provide a device for the emission of acoustic pulses that is easy and economical to manufacture at an industrial level.

This aim and these objects, as well as other objects which will become evident from the following description and the attached drawings, are achieved, according to the invention, by a device for the emission of acoustic pulses, according to claim 1 and the related dependent claims, proposed in the sequel.

In a general definition, the device for the emission of acoustic pulses, according to the invention, comprises a containment structure having at least one reversibly deformable wall (preferably elastically deformable) and intended to be placed in contact with a means of propagation of the acoustic pulses (for example sea water).

The containment structure is arranged in such a way as to define, at least partially, an internal volume of the device which is segregated with respect to the aforementioned means of propagation of the acoustic impulses.

Said internal volume is filled, at least partially, with a conductive medium in the fluid state (preferably of liquid) having a controlled electrical conductivity lower than or equal to 10 mS, at a temperature of 20 ° C.

The device, according to the invention, also comprises an acoustic pulse generation unit comprising at least one pair of electrodes which includes a first electrode (or cathode electrode) and a second electrode (or anode electrode) spaced apart. The aforesaid first and second electrodes are arranged so as to be in contact with said conductive means and spaced from each other. The separation space between said first and second electrodes is therefore occupied by said conductive means.

According to the invention, the aforesaid first and second electrodes are electrically connectable to a power source and are adapted to receive electrical energy (for example a current pulse) from the aforesaid power source so that an electric discharge is generated between said first and second electrode and, consequently, an acoustic impulse is generated. The latter is transmitted from said conductive medium to said means of propagation of the acoustic impulses through the deformable wall of the containment structure.

Preferably, the aforesaid conductive medium has an electrical conductivity lower than or equal to 8 mS, at a temperature of 20 ° C.

Preferably, the aforesaid conductive medium is in the liquid state and consists of a solution of water and sodium chloride, with a sodium chloride concentration lower than or equal to 10 g / liter.

Preferably, the aforesaid conductive medium consists of a solution of water and sodium chloride, with a sodium chloride concentration lower than or equal to 5 g / liter.

Preferably, in said group for generating the acoustic pulses, at least one of the aforementioned first and second electrodes (or anode electrodes) is made of copper.

Preferably, in said group for generating the acoustic pulses, the aforementioned second electrode (or anode electrode) has an enlarged shape with respect to said first electrode (or cathode electrode).

According to a preferred embodiment, said second electrode (or anode electrode) has the shape of a rotation paraboloid, advantageously with a concavity facing the deformable wall of said containment structure. Said first electrode (or cathode electrode) has an elongated shape and is arranged along the main axis of symmetry of said paraboloid. According to this embodiment, the containment structure comprises a deformable sheet of plastic material coupled to the second electrode at a free edge of said paraboloid so as to define, in cooperation with said second electrode, an internal volume for containing said conductive medium.

In a further aspect, the present invention refers to an ecometric apparatus comprising the device for the emission of acoustic pulses, according to the invention.

Preferably, this ecometric apparatus is an ecometric apparatus for submarine and inland water exploration.

Further characteristics and advantages of the device for the emission of acoustic pulses, according to the invention, can be better perceived by referring to the description given below and to the attached figures, provided for purely illustrative and non-limiting purposes, in which: - the figure 1 schematically illustrates the device for emitting acoustic pulses, according to the invention; And

- Figures 2-3 schematically illustrate an embodiment of the device for emitting acoustic pulses, according to the invention; And

- Figure 4 schematically illustrates some experimental measurements relating to the operation of the device for emitting acoustic pulses, according to the invention, in the embodiment of Figures 2-3.

With reference to the aforementioned figures, the present invention refers to a device 1 for the emission of acoustic pulses.

The device 1 is particularly suitable for use in ecometric apparatuses intended to carry out the prospection of submarine or underwater soil in general and will be described with particular reference to this type of application for obvious reasons of brevity and, in any case, without wanting to limit its scope. application scope.

The device 1 can, in fact, find use in ecometric apparatuses of any type, for example in ecometric apparatuses for industrial, military, medical applications, and so on.

With reference to the aforementioned figures, the device 1 preferably comprises a support structure 4 adapted to support and maintain in position some components of the device itself.

According to some embodiments of the invention, for example when the device 1 is intended to be used in an ecometric apparatus for underwater and inland water exploration, the support structure 4 can advantageously comprise or be connected to one or more floating elements 40 or similar.

According to the invention, the device 1 comprises an acoustic pulse generation unit 3 having at least one pair of electrodes which includes a first electrode 31 and a second electrode 32 spaced apart.

In the operation of the device 1, the first electrode 31 (or cathode electrode) is advantageously intended to be placed at a positive electric voltage while the second electrode 32 (or anode electrode) is intended to be grounded or to an analogous reference voltage.

Preferably, the acoustic impulse generation unit 3 is operatively connected to the support structure 4, for example by providing suitable elements (not shown) for mechanical connection and electrical insulation (not shown).

In principle, the first and second electrodes 31, 32 can have any shape, according to requirements.

Preferably, the second electrode 32 has an enlarged shape with respect to the first electrode 31, for example as in the preferred configuration illustrated in Figures 2-3.

Preferably, the first electrode 31 has an elongated shape with a substantially point-like transverse dimension (i.e. very small or negligible with respect to length).

According to the invention, the device 1 comprises a containment structure 2 which can be operatively connected to the support structure 4 and / or to the pulse generation unit 3.

The containment structure 2 comprises at least one wall 21 mechanically deformable in a reversible way and intended to be placed in contact with a propagation medium (not shown) of the acoustic pulses.

When used in an ecometric apparatus for underwater and inland water exploration, the containment structure 2 can be immersed at least partially, so that the deformable wall 21 is in contact with sea or lake water (which, in this case, constitutes the means of propagation of acoustic impulses).

Preferably, the deformable wall 21 of the containment structure 2 is made in such a way as to be mechanically deformable in a reversible way (for example elastically deformable) with respect to a pressure wave coming from inside the device 1.

Preferably, at least the deformable wall 21 of the containment structure 2 is made of an electrically insulating material.

Preferably, in particular when the device 1 is intended to be used in an ecometric apparatus for underwater and inland water exploration, the containment structure 2 is advantageously made of an impermeable material, at least in correspondence with its parts intended to come into contact with the water.

In general, the containment structure 2 is able to define, at least partially, an internal volume 20 of the device segregated with respect to the means of propagation of the acoustic pulses. In principle, the containment structure 2 can have any shape, according to requirements.

As better illustrated below, according to some embodiments of the invention (Figure 2), the containment structure 2 defines the internal volume 20 in cooperation with parts of the pulse generation unit 3, in particular with the second electrode 32 ( anode) of the latter.

According to other embodiments of the invention (not shown), the containment structure 2 consists of a separate container or defines the internal volume 20 in cooperation with (electrically insulating) parts of the support structure 4.

According to the invention, the aforementioned internal volume 20 (defined, at least in part, by the containment structure 20) is filled, at least partially, with a conductive medium 200 having controlled electrical conductivity.

Advantageously, the conductive medium 200 is in the state of fluid, preferably of liquid. According to the invention, the first and second electrodes 31, 32 are arranged so as to be in contact with the conductive medium 200 and so that the separation space between said electrodes is occupied by said conductive medium. In this way, the conductive means 20 is intended to be subjected to an electric field between the electrodes 31, 32, when an electrical voltage differential is applied to the latter.

According to some embodiments of the invention (Figure 1), the electrodes 31, 32 are arranged inside the internal volume 20 so as to be immersed in the conductive medium 200.

According to some embodiments of the invention (Figure 2), the first electrode 31 (cathode electrode) is advantageously arranged inside the internal volume 20 so as to be immersed in the conductive medium 200 while the second electrode 32 (anode electrode) it delimits the internal volume 20 in cooperation with the containment structure 2 and is therefore placed in contact with the conductive medium itself.

Preferably, at least one of said first and second electrodes 31, 32 is made of copper. According to further preferred embodiments, both electrodes 31, 32 are made of copper.

According to the invention, the conductive medium 200 has electrical conductivity less than or equal to 10 mS at a reference temperature of 20 ° C.

Preferably, the conductive medium 200 has an electrical conductivity lower than or equal to 8 mS, at the temperature of 20 ° C.

According to a preferred embodiment of the invention, the conductive medium 200 is in the liquid state.

Preferably, the conductive medium 200 consists of a solution of water and sodium chloride, with a sodium chloride concentration lower than or equal to 10 g / liter.

Even more preferably, the conductive medium 200 consists of a solution of water and sodium chloride, with a sodium chloride concentration lower than or equal to 5 g / liter. According to the invention, the electrodes 31, 32 of the acoustic pulse generation unit 3 are electrically connectable to an electrical power source 6.

The electrical power source 6 is adapted to supply an impulsive quantity of electrical energy (current pulse) to the electrodes 31, 32 of the device 1.

When the aforesaid electrodes receive voltage from the power source 6, an electric discharge is formed between the electrodes themselves and, consequently, an acoustic impulse is generated which is transmitted from the conductive medium 20 to the aforementioned means of propagation of the acoustic impulses through the deformable wall. 21 of the containment structure 2.

The aforesaid electric discharge, in fact, causes the formation of a region in the plasma state in the conductive medium 200 in correspondence with the electrodes 31, 32.

This region of conductive medium in the plasma state expands during the electrical discharge and collapses suddenly when the electrical discharge is exhausted at the end of the electrical energy impulse provided by the power source 6.

The process of formation, expansion and subsequent collapse of this region of conductive medium in the plasma state generates an acoustic impulse which is transmitted to the propagation medium of the acoustic impulses through the deformable wall 21.

Preferably, the electric power source 6 comprises a positive terminal T1 electrically connectable to the first electrode 31 (cathode electrode) and a negative terminal T2 electrically connectable to the second electrode 32 (anode electrode).

In principle, the power source 6 is not included in the device 1. It can be advantageously arranged on the field of use of the device 1 to ensure its operation.

According to some embodiments of the invention, however, the power source 6 could be part of the device 1 and transportable with it.

In general, the power source 6 can be of the capacitive type. For example, it may comprise a bank of power capacitors.

Figures 2-3 show a preferred embodiment of the device 1 for emitting acoustic pulses, according to the invention.

According to this embodiment in Figure 2, the first electrode 31 (cathode electrode) consists of an elongated electrically conductive element (preferably made of copper or tungsten or other metal with high electrical conductivity and high corrosion resistance), for example a cylindrical element conductive with substantially point-like bases (i.e. with very small or negligible dimensions compared to the length of the cylindrical element itself).

The first electrode 31 comprises a first free end 311 and a second end 312, opposite the aforementioned first end 311 and electrically connectable to the positive terminal of the power source 6.

Advantageously, the acoustic pulse generation unit 3 comprises a hollow insulator element 33, also having a substantially cylindrical shape and coupled coaxially with the first electrode 31 so as to cover the latter for part of its length and electrically isolate it with respect to the electrode 32.

The second electrode 32 (anode electrode) consists of a conductive element (preferably made of copper) having the shape of a rotation paraboloid, with a vertex point P, a focus point F and an axis of symmetry A passing through the points of vertex P and of focus F. The second electrode 32 comprises a coupling edge 320 which delimits its concavity in a distal position with respect to the vertex point P. This coupling edge is mechanically connected to the support structure 4 by means of suitable connection means (e.g. electrically insulating mechanical connectors).

The second electrode 32 is electrically connected directly to the terminal T2 (for example negative or to ground) of the power source 6 by means of an electrical connection element of a known type (for example an electric clamp), advantageously passing, at least partially, through the element isolator 33.

According to the embodiment of Figure 2, the first electrode 31 is arranged along the axis of symmetry A.

Advantageously, the first electrode 31 and the insulator element 33 are operatively associated with the second electrode 32 at the vertex point P of the latter. In particular, they are designed to pass through a hole 321 made at the vertex point P of the electrode 32.

Advantageously, the first electrode 31 and the insulator element 33 are mechanically connected to the second electrode 32 by means of mechanical connection of a known type (for example one or more mechanical flanges - figure 3).

According to the aforementioned embodiment (Figure 2), the containment structure 2 is constituted by a flexible sheet of plastic material coupled (by means of mechanical coupling means of known type) to the second electrode 32 in correspondence with the coupling edge 320 of the latter. .

The containment structure 2 thus defines, in cooperation with the second electrode 32 (anode electrode), the internal volume 20 for containing the conductive medium 200.

The operation of the device 1 for the emission of acoustic pulses, in the embodiment of figures 2-3, is now briefly illustrated.

At the beginning of an operating cycle, the power source 6 is electrically connected to the electrodes 31, 32 in response to a command from the user.

The power source 6 supplies a current pulse having a predefined duration (for example a few ms) which causes the formation of an electric discharge in the conductive medium 200 between the aforesaid electrodes.

The electrical discharge in the conductive medium 200 causes the formation of a region in which the conductive medium 200 changes to the plasma state.

For the entire duration of the current pulse provided by the power source 6, the region of the conductive medium 200 in the plasma state expands in the volume occupied by the aforementioned conductive medium.

Experimental tests have shown that this region of conductive medium in the plasma state does not expand uniformly but has preferential expansion lobes along the inner surface of the paraboloid-shaped electrode 32.

At the end of the current pulse provided by the power source 6, since the triggered electric discharge is no longer powered, the region of conductive medium 200 in the plasma state suddenly collapses.

The process of expansion and collapse of the region of conductive medium 200 in the plasma state generates an acoustic impulse which propagates towards the deformable wall 21 and is transmitted to the propagation medium of the acoustic impulses (for example sea water) through the deformable wall 21 which it deforms elastically.

Experimental tests have shown how the generated acoustic pulse propagates substantially along the axis of symmetry A of the paraboloid-shaped electrode 32 (anode electrode).

It is evident that the expansion and collapse process of the conductive medium region 200 in the plasma state does not involve any substantial variation in the overall volume of the conductive medium 200.

Figure 4 illustrates some measurements made during an experimental operation test of the device 1 for the emission of acoustic pulses, in the embodiment of figure 2.

The experimental test was carried out in a tank structure filled with fresh water in which the device for the emission of acoustic pulses was partially immersed. The internal volume 20 of the device 1 was filled with a solution of water and sodium chloride, with a sodium chloride concentration lower than 5 g / liter.

The power source 6 (bank of capacitors) has been arranged so as to supply a voltage of 4.5 kV between the terminals T1, T2 (and therefore to the electrodes 31, 32).

The curve C1 of figure 4 illustrates the trend of the current supplied by the power source 6 (measured with an ammeter) during an operating cycle of the device (t = 0, instant of activation of the power source 6 and start of the operating cycle ).

It is evident the presence of an IC pulse lasting about 2 ms centered at the instant t = 2ms.

Curve C2 of figure 4 illustrates an audiometric measurement carried out by means of a hydrophone placed about 1.5 m from the device 1 and immersed in the propagation medium of the acoustic impulses (fresh water) in which the device 1 was, in turn, absorbed.

It is evident the presence of a first AC1 acoustic impulse with reduced duration (in the order of a few ฀ s) and high amplitude (of the order of 80-100 dB) near the instant t = 12 ms. This acoustic impulse constitutes the acoustic impulse generated by the device 1 and transmitted to the propagation medium of the acoustic impulses.

Note the presence of a second AC2 pulse with a lower amplitude than the first AC1 pulse, mentioned above. This acoustic impulse represents the echo of the first AC1 acoustic impulse generated by the reflection of this acoustic impulse in correspondence with the walls of the tank structure.

The device for the emission of acoustic impulses, according to the invention, has considerable advantages over the known art.

A very important aspect of the present invention is represented by the fact that the electric discharge between the electrodes 31, 32 is generated in a conductive medium 200 having relatively low conductivity, according to the values indicated above.

It has been verified that this solution allows to obtain an improved quality of the generated acoustic impulse. The latter, in fact, with the same power used, has a shorter duration and higher amplitude than an acoustic pulse generated by a traditional "sparker" device with the electrodes immersed in water (typically with a duration of several ms). It is pointed out that, in a conductive medium 200 with relatively low conductivity, the region of the conductive medium in the plasma state expands more slowly than in a traditional "sparker" device. This allows to considerably reduce the presence of spurious acoustic components generated by turbulence of the plasma region during the expansion phase.

A further important aspect of the device for the generation of acoustic pulses, according to the invention, consists in the use, in the generation unit 3 of the acoustic pulses, of electrodes 31, 32 having a different shape, with the second electrode 32 (anode electrode ) having an enlarged shape with respect to the first electrode 31 (cathode electrode).

First of all, this solution allows to significantly improve the control of the direction of the acoustic impulse generated. For example, in the embodiment of Figures 2-3, the concavity of the anode electrode 32 determines a concentration of the acoustic energy in a specific direction, similar to the phenomenon of concentration of the explosive energy typical of a hollow charge (effect Munroe). This allows to obtain a strongly directional acoustic impulse, which propagates along the axis of symmetry A of the paraboloid. Furthermore, the solution illustrated above allows to obtain acoustic pulses with an even greater amplitude, for the same electrical power used. For example, in the embodiment of Figures 2-3, the concavity of the anode electrode 32 determines the expansion of the region of conductive medium 200 in the plasma state towards the outer edge 320 of the electrode itself (according to the above-mentioned lobes expansion preferentials) by increasing the volume occupied by the region of conductive medium 200 in the plasma state and, therefore, the power of the acoustic pulse generated, for the same electrical power used.

The device for generating acoustic pulses, according to the invention, is thus able to offer very high performances as regards the power and quality (in terms of duration and amplitude) of the acoustic pulses generated and the control of the emission direction. of the latter.

If used in an ecometric apparatus for underwater and inland water exploration, the device for generating acoustic pulses, according to the invention, allows to obtain "acoustic images" of the underwater soil of very high quality, typically with resolution values lower than 0.2m for vertical resolution. It should be noted that these resolution values cannot be obtained in any way with echometric devices equipped with traditional “sparker” devices for generating acoustic impulses.

The device for generating acoustic pulses, according to the invention, is easy to use in practice and does not require the performance of complex calibration or tuning procedures during its operational life.

The device for generating acoustic pulses, according to the invention, has a very compact structure that can be easily manufactured at an industrial level with known types of components, at competitive costs with the available solutions of the known art.

Claims (10)

CLAIMS 1. Device (1) for the emission of acoustic impulses characterized by the fact of including: - a containment structure (2) having at least one wall (21) reversibly deformable (21) and intended to be placed in contact with a means of propagation of the acoustic impulses, said containment structure defining, at least partially, an internal volume (20 ) segregated with respect to said means of propagation of the acoustic pulses and filled, at least partially, with a conductive medium (200) in the fluid state having an electrical conductivity lower than or equal to 10 mS, at a temperature of 20 ° C; - an acoustic pulse generation unit (3) comprising at least one pair of electrodes which includes a first electrode (31) and a second electrode (32) spaced apart, said first and second electrodes being arranged so as to be in contact with said conductive means (200); wherein said first and second electrodes (31, 32) are electrically connectable to a power source (6) and are adapted to receive electrical energy from said power source so that an electric discharge is generated between said first and second electrodes ( 3) and, consequently, an acoustic pulse is generated which is transmitted to said means of propagation of the acoustic pulses through the deformable wall (21) of said containment structure. 2. Device according to claim 1, characterized in that said conductive medium (200) has an electrical conductivity lower than or equal to 8 mS, at a temperature of 20 ° C. 3. Device according to one or more of the preceding claims, characterized in that said conductive medium (200) is a liquid. 4. Device according to claim 3, characterized in that said conductive medium (200) consists of a solution of water and sodium chloride, with a sodium chloride concentration lower than or equal to 10 g / liter. 5. Device according to claims 2 to 4, characterized in that said conductive medium (200) is a solution of water and sodium chloride, with a sodium chloride concentration lower than or equal to 5 g / liter. 6. Device according to one or more of the preceding claims, characterized in that said second electrode (32) has an enlarged shape with respect to said first electrode. 7. Device, according to claim 6, characterized in that said second electrode (32) has the shape of a paraboloid of rotation and said first electrode (31) has an elongated rectilinear shape, said first electrode being arranged along a main axis of symmetry ( A) of said paraboloid. 8. Device, according to claim 7, characterized by the fact that said containment structure (2) comprises a deformable sheet (21) of plastic material coupled to said second electrode (32) at a free edge (320) of said paraboloid. 9. Ecometric apparatus characterized by the fact of comprising a device (1) for the emission of acoustic pulses, according to one or more of the preceding claims. 10. Ecometric apparatus, according to claim 9, characterized in that it is an ecometric apparatus for marine and inland water exploration.