CN113900081A - Underwater acoustic transducer capable of measuring temperature on line - Google Patents

Abstract

The invention provides an underwater acoustic transducer capable of measuring temperature online, which mainly comprises a transducer shell, a plurality of fiber bragg grating temperature sensors, a test optical fiber and a watertight socket, wherein the fiber bragg grating temperature sensors are fixed on the surface to be measured in the transducer, the test optical fiber is led out from the tail part of the fiber bragg grating temperature sensors, and the test optical fiber penetrates out of the transducer through the watertight socket to be connected with wavelength demodulation equipment to form a test optical path. The invention has the beneficial effects that: the problem of the inside temperature unknown of underwater transducer during operation is solved, can be used to provide technical support for verifying, analyzing, optimizing transducer thermal behavior, also can avoid the risk that the transducer damages because of the high temperature. The transducer capable of measuring temperature on line has the characteristics of wide applicability and high temperature detection precision.

Description

Underwater acoustic transducer capable of measuring temperature on line

Technical Field

The invention belongs to the technical field of underwater acoustic transducers, and mainly relates to an underwater acoustic transducer capable of measuring temperature on line.

Background

An underwater acoustic transducer is an important device for generating or receiving acoustic signals in a sonar system, and the main function of the underwater acoustic transducer is to realize interconversion between electric energy and acoustic energy. The conversion of electrical energy into acoustic energy radiated into the water is called a transmitting transducer, while the conversion of received acoustic energy into electrical energy is called a receiving transducer or hydrophone. During the energy conversion process of the transducer, the result of partial energy conversion into internal energy is inevitable. In practical applications, only temperature variations inside the transmitting transducer are usually of interest. This is because the hydrophone receives acoustic energy typically in the milliwatts range, where the energy converted into internal energy is negligible. The transmitting transducer is used as a component for radiating acoustic energy outwards, and a considerable part of input electric energy is converted into internal energy. Meanwhile, due to the difference between the driving materials and the driving modes of the transducers, the difference between the electroacoustic conversion efficiencies of different types of transducers can reach an order of magnitude, and therefore the temperature change caused by the accumulation of internal energy inside the transmitting transducer is not negligible.

When the temperature inside the transducer rises to the curie temperature, the active material of the transducer will lose piezoelectric or magnetostrictive properties, rendering the transducer inoperable. More seriously, the piezoelectric properties of the piezoelectric active material do not recover when the transducer temperature is reduced back to room temperature. The operating temperature of the piezoelectric material is therefore safe at least below half the curie point. Even if the temperature rise of the transducer is in a safe range, parameters such as dielectric constant, coupling coefficient and the like of the active material can change along with the temperature rise, and finally the electroacoustic performance of the transducer is unstable. In addition, passive materials such as glue layers, polyurethane watertight layers, etc. can produce drastic changes in physical properties due to overheating, thereby affecting the stability and reliability of the transducer, and even causing permanent damage.

Through the on-line monitoring of the temperature of the transducer, the thermal performance of various transducers with different electroacoustic conversion efficiencies can be researched, and the design method of the transducers with different types and different materials can be mastered. Meanwhile, online temperature measurement has important significance for mastering the thermal limit of the transducer and improving the design reliability of the transducer. Further, for the application of the transducer, for a user of the transducer, especially for a user who is not familiar with the structure and performance of the underwater acoustic transducer, the online temperature measurement result is used as important additional data for judging the working state of the transducer, which is beneficial to the safe use of the transducer.

Disclosure of Invention

The invention aims to overcome the defects in the prior art and provide an underwater acoustic transducer capable of measuring temperature on line, which can be applied to a low-frequency active sound source and is an important part used in a sonar system.

The object of the present invention is achieved by the following technical means. The utility model provides an underwater acoustic transducer that can online temperature measurement, mainly includes transducer shell, a plurality of bragg fiber grating temperature sensor, test optic fibre and watertight socket, bragg fiber grating temperature sensor be fixed in the inside surface that awaits measuring of transducer, test optic fibre is drawn forth to bragg fiber grating temperature sensor afterbody, and test optic fibre is worn out the transducer through the watertight socket and is connected with wavelength demodulation equipment, constitutes the test light path. When the transducer is electrified to work, the transducer radiates sound energy outwards, and meanwhile, part of electric energy is converted into internal energy to cause the internal temperature of the transducer to rise. The Bragg fiber grating temperature sensor detects that the optical signal changes after the temperature changes, the wavelength demodulation equipment demodulates the received optical signal into temperature information, and the temperature information of the transducer is displayed in a computer.

The type of transducer described in the present invention is not limited and the type of transducer used in practice will depend primarily on the transducer that is desired to be monitored. Because Bragg fiber grating temperature sensor is the probe structure, small in size can fill in the narrow and small inner space of transducer, carries out temperature monitoring to the dead angle to can not influence the normal work of transducer, consequently transducer inner structure need not make too much modification for temperature monitoring device. A plurality of fiber bragg grating temperature sensors are arranged in the energy converter, and the temperature distribution of a plurality of temperature measuring points in the energy converter can be accurately measured. Meanwhile, in order to monitor the temperature change of the transducer on line, the bragg fiber grating temperature sensor needs to continuously exchange data with a testing end through the optical fiber, so that the watertight structure and the filling mold of the transducer need to be improved for the temperature testing optical fiber.

The transducer is characterized in that the transducer is of a basic structure of an underwater acoustic transducer consisting of a transducer shell, a piezoelectric stack, an upper cover plate, a lower cover plate, a watertight connector, electrodes and a watertight encapsulating layer, the upper cover plate and the lower cover plate are arranged at the upper end and the lower end of the transducer shell and form a sealed cavity inside the transducer shell, the watertight encapsulating layer is arranged outside the upper cover plate and the lower cover plate, the piezoelectric stack, a Bragg fiber bragg grating temperature sensor and the electrodes are arranged in the cavity, and the watertight connector and a watertight socket are arranged on the upper cover plate; the piezoelectric stack is a driving structure of the transducer and is formed by stacking piezoelectric single crystal wafers with polarized thicknesses in opposite polarization directions, all the piezoelectric single crystal wafers are connected in parallel and then are electrified with alternating current, the piezoelectric stack vibrates in a reciprocating mode along the stacking direction, and the electrodes are thin copper sheets and are clamped between the two piezoelectric single crystals and used for communicating silver coatings on the surfaces of the piezoelectric single crystal wafers and wires.

The fiber bragg grating temperature sensor consists of a fiber bragg grating, a protective shell, a switching tube, a fiber sheath and an optical fiber, wherein the fiber sheath and the optical fiber form a test optical fiber, and the switching tube is connected with the protective shell and the fiber sheath; the Bragg fiber grating is positioned in the protective shell, and the protective shell is closely contacted with the surface to be measured; one end of the protective shell is closed, the other end of the protective shell is led out of the test optical fiber, and the Bragg optical fiber grating is in a stress free state in the protective shell.

The Bragg fiber grating temperature sensor is fixed on the surface to be measured in the transducer in a bonding, clamping or embedding mode and the like.

The protective shell is made of hard materials with good heat-conducting property, such as iron, copper and the like.

The watertight socket is formed by a metal round pipe, a protection pipe and a groove, the watertight socket is made of corrosion-resistant materials, a through hole is formed in the center of the watertight socket, and the watertight socket can pass through a plurality of test optical fibers. The position of the test optical fiber passing through the upper cover plate of the transducer is provided with a watertight socket so as to prevent the test optical fiber from damaging the watertight structure of the transducer. The middle section outside the watertight socket is provided with a fixed platform, and the fixed platform is arranged between the upper cover plate and the watertight sealing layer and is used for fixing the installation depth of the watertight socket and bearing the water pressure borne by the watertight socket; the end of the watertight socket facing the outside of the transducer is provided with a flexible protection tube connected with the metal round tube, so that the abrasion or the breakage of the test optical fiber at the metal right-angle position of the through hole of the watertight socket in the using process is avoided. The metal round tube penetrates through the test optical fiber and is plugged by hard waterproof glue, so that the functions of watertight and fixing the test optical fiber are achieved. An O-shaped sealing ring is arranged on the groove and used for sealing the upper cover plate and the watertight socket.

The internal transmission signal of the test optical fiber is an optical signal, the optical signal is input at one end of the test optical fiber, the Bragg fiber grating temperature sensor transforms the optical signal transmitted by the test optical fiber into an optical signal containing temperature information, and the transformed optical signal is reflected back along the test optical fiber.

The invention has the beneficial effects that:

1. the problem of the inside temperature unknown of underwater transducer during operation is solved, can be used to provide technical support for verifying, analyzing, optimizing transducer thermal behavior, also can avoid the risk that the transducer damages because of the high temperature. The transducer capable of measuring temperature on line has the characteristics of wide applicability and high temperature detection precision.

2. Based on the advantages of small volume and strong anti-electromagnetic signal interference capability of the Bragg fiber grating temperature sensor, the Bragg fiber grating temperature sensor is arranged in the transducer, the problem of signal water output transmission is solved, and the real-time monitoring of the temperature of the key part of the transducer is realized. The design can not influence the structural design and the vibration characteristic of the transducer, and can also avoid the interference of a strong electric field in the transducer on the temperature test accuracy.

Drawings

FIG. 1 is a cross-sectional view of a transducer;

FIG. 2 is a schematic view of a transducer;

FIG. 3 is a partial cross-sectional view of a transducer water-tight socket portion;

FIG. 4 is a schematic structural diagram of a Bragg fiber grating temperature sensor;

FIG. 5 is a schematic view of an upper cover plate of the transducer;

FIG. 6 is a schematic view of a watertight socket.

Description of reference numerals: the device comprises a transducer shell 1, a piezoelectric stack 2, an upper cover plate 3, a lower cover plate 4, a watertight connector 5, an electrode 6, a watertight potting layer 7, a Bragg fiber grating temperature sensor 8, a test optical fiber 9, a watertight socket 10, a Bragg fiber grating 11, a protective shell 12, an adapter tube 13, an optical fiber sheath 14, a through hole A15, a through hole B16, a metal round tube 17, a fixed platform 18, a protective tube 19, a groove 20, a mounting hole 21, an optical fiber 22 and decoupling materials 23.

Detailed Description

The invention will be described in detail below with reference to the following drawings:

the transducer structure for online monitoring of internal temperature changes is shown in figure 1, and mainly comprises a transducer shell 1, a piezoelectric stack 2, an upper cover plate 3, a lower cover plate 4, a watertight connector 5, an electrode 6, a watertight potting layer 7, a Bragg fiber grating temperature sensor 8, a test optical fiber 9 and a watertight socket 10. The transducer shell 1, the piezoelectric stack 2, the upper cover plate 3, the lower cover plate 4, the watertight connector 5, the electrode 6 and the watertight potting layer 7 constitute the basic structure of the underwater acoustic transducer to be monitored for temperature, and it should be noted that the transducer capable of monitoring temperature according to the present invention includes, but is not limited to, the transducer structure described in this example, and this example is only used to illustrate the working principle of the transducer capable of monitoring internal temperature change online. The transducer housing 1 is made of aluminum alloy and functions to vibrate and sound under the driving of the piezoelectric stack 2. The piezoelectric stack 2 is a driving structure of the transducer and is formed by stacking piezoelectric single crystal wafers with thickness polarization in opposite polarization directions, all the piezoelectric single crystal wafers are connected in parallel and then are electrified with alternating current, and the piezoelectric stack 2 vibrates in a reciprocating mode along the stacking direction. The upper cover plate 3 and the lower cover plate 4 are mainly used for maintaining the watertight environment inside the transducer, and the upper cover plate 3 is also designed with a through hole A15 and a through hole B16 for installing the watertight connector 5 and the watertight socket 8. The watertight connector 5 is an interface between the transducer and the output line of the power amplifier and is an inlet of the electric energy input transducer. The electrode 6 is a thin copper sheet and is clamped between the two piezoelectric single crystals to play a role in communicating the silver plating layer on the surface of the piezoelectric single crystal sheet with a lead. The watertight encapsulating layer 7 is a structure formed by pouring polyurethane, and mainly maintains the upper cover plate 3 and the lower cover plate 4, the Bragg fiber grating temperature sensor 8 is fixed on the inner surface of the transducer in an adhesive mode, and for testing accuracy, the protective shell of the Bragg fiber grating temperature sensor 8 needs to be in close contact with the surface to be tested. The test optical fiber 9 is led out from the tail part of the Bragg optical fiber grating temperature sensor 8, and the transducer is led out through the watertight socket 10 to be connected with the wavelength demodulation equipment, so that a test optical path is formed. The watertight socket 10 is inserted straight into the through hole B16 of the upper cover plate 3 and fixed by potting urethane.

Fig. 2 is a schematic structural diagram of the bragg fiber grating temperature sensor 8. The fiber bragg grating temperature sensor 8 is composed of a fiber bragg grating 11, a protective shell 12, an adapter tube 13, a fiber sheath 14 and an optical fiber 22. The bragg fiber grating 11 is a doped-undoped periodic structure formed in the optical fiber 22 by processing, which is capable of reflecting light waves of a specific wavelength. At the same time, stress variations and temperature variations can change the wavelength at which the reflection of the structure acts. The protective shell 12 is a metal thin-wall circular tube with one end sealed, and the protective shell 12 is in close contact with the surface to be measured. The bragg fiber grating 11 is in a completely free state in the protective housing 12, is not disturbed by external stress, and is only sensitive to the ambient temperature. Meanwhile, the Bragg fiber grating 11 is not influenced by environmental stress and has good long-term reliability. The adapter tube 13 is used to connect the protective housing 12 and the fiber jacket 14, the fiber jacket 14 and the optical fiber 22 constituting the test fiber 9. The single end of the Bragg fiber grating temperature sensor 8 is led out, the temperature measurement precision is high and can reach 0.1 ℃. The testing and the conduction of the Bragg fiber grating temperature sensor 8 are realized by optical signals, so that the interference of a strong electric field or a magnetic field in the transducer on a testing result is avoided.

The bragg fiber grating has a reflecting effect on light waves of a specific wavelength, and the wavelength of the reflected light waves is related to the stress and the temperature of the bragg grating. The protective shell protects the Bragg fiber grating in the metal thin-wall circular tube, and the Bragg fiber grating is prevented from changing the wavelength of the reflected light wave and being damaged due to stress. Therefore, when the temperature of the fiber bragg grating temperature sensor changes, the wavelength of the reflected light wave of the fiber bragg grating temperature sensor changes accordingly. Therefore, the packaged fiber Bragg grating temperature sensor can determine the change of the environment temperature by testing the wavelength change of the fiber Bragg grating reflected light as long as the thermal expansion coefficient and the thermo-optic coefficient are obtained through calibration.

Fig. 5 is a schematic view of the transducer upper cover plate 3. The upper cover plate is provided with a through hole A15 for mounting a watertight connector and a through hole B16 for mounting a watertight socket.

Fig. 3 and 6 are schematic structural views of the watertight socket 10. The watertight socket 10 is composed of a metal round pipe 17, a protection pipe 19, a groove 20 and a mounting hole 21, a fixing platform 18 is arranged at the middle section of the outside of the watertight socket 1, and the fixing platform 18 is arranged between the upper cover plate 3 and the watertight sealing layer 7 and used for fixing the mounting depth of the watertight socket and bearing the water pressure borne by the watertight socket. The optical fiber is passed through the inside of the metal round tube 17, and the residual space is blocked by hard waterproof glue. The fixing platform 18 is engaged with the outer surface of the upper cover plate 3 when the metal round tube 17 is inserted into the through hole B16, and plays a role of bearing the water pressure and fixing the watertight socket 10. The protection tube 19 is to protect the optical fiber led out from the metal round tube 17 from being worn or broken at the mouth of the metal round tube 17 during measurement and transportation. The groove 20 is provided with an O-shaped sealing ring and is matched with the mounting hole 21 for watertight treatment of the transducer of the anhydrous sealing and filling layer 7; the decoupling material 23 mainly serves to isolate vibrations between the housing 1 and the cover plate 3.

6. The underwater acoustic transducer capable of measuring temperature online according to claim 1 or 2, wherein: the watertight socket 10 comprises a metal round pipe 17, a protection pipe 19 and a groove 20, wherein the protection pipe 19 connected with the metal round pipe 17 is arranged at one end, facing the outside of the transducer, of the watertight socket 10, the metal round pipe 17 penetrates through the test optical fiber 9 and then is plugged by hard waterproof glue, and an O-shaped sealing ring is arranged on the groove 20 and used for sealing the upper cover plate 3 and the watertight socket 10.

In this embodiment, the flextensional transducer is used as an object, and the specific assembly process of the transducer capable of monitoring the temperature change on line provided by the invention comprises the following steps:

step 1: firstly, the piezoelectric single crystal pieces are stacked and bonded by epoxy resin glue to form the piezoelectric stack 2. The fiber bragg grating temperature sensor 8 is then glued to the piezoelectric stack 2 or transducer housing 1 surface at a point where testing is desired. The piezoelectric crystal stack 2 is then placed in the transducer housing 1.

Step 2: after the optical fiber is inserted into the watertight socket 10, the watertight socket is sealed with a hard waterproof adhesive, and the watertight connector 5 and the watertight socket 10 are mounted in the upper cover plate 3. And then the optical fiber led out from the tail part of the fiber Bragg grating temperature sensor 8 is welded with the optical fiber in the watertight socket 10.

And step 3: the upper cover plate 3 and the lower cover plate 4 are closed at the upper end and the lower end of the transducer shell 1, and the upper cover plate 3, the lower cover plate 4 and the transducer shell 1 are sealed and sealed watertight by polyurethane through a mould.

The invention improves the existing design of the transducer, and can monitor the temperature change of the transducer in real time by internally arranging the Bragg fiber grating temperature sensor. On one hand, the dynamic working characteristics of the transducer can be mastered, and particularly for certain temperature-sensitive transducers, convenience is provided for the thermal performance research of the transducer; on the other hand, for the transducer with larger heat productivity, the real-time monitoring of the temperature of the transducer is beneficial to mastering the working environment of the transducer, and the damage to the transducer caused by overhigh temperature is avoided.

It should be understood that equivalent substitutions and changes to the technical solution and the inventive concept of the present invention should be made by those skilled in the art to the protection scope of the appended claims.

Claims (6)

1. An underwater acoustic transducer capable of measuring temperature online is characterized in that: the optical fiber Bragg grating temperature sensor mainly comprises an energy converter shell (1), a plurality of optical fiber Bragg grating temperature sensors (8), a test optical fiber (9) and a watertight socket (10), wherein the optical fiber Bragg grating temperature sensors (8) are fixed on the surface to be tested inside the energy converter, the test optical fiber (9) is led out from the tail part of the optical fiber Bragg grating temperature sensors (8), and the test optical fiber (9) penetrates out of the energy converter through the watertight socket (10) to be connected with wavelength demodulation equipment to form a test optical path.

2. The underwater acoustic transducer capable of measuring temperature online according to claim 1, wherein: the energy converter is characterized in that the energy converter is a basic structure of the underwater acoustic transducer, and the basic structure comprises an energy converter shell (1), a piezoelectric stack (2), an upper cover plate (3), a lower cover plate (4), a watertight connector (5), an electrode (6) and a watertight sealing layer (7), wherein the upper cover plate (3) and the lower cover plate (4) are arranged at the upper end and the lower end of the energy converter shell (1) and form a sealed cavity inside, the watertight sealing layer (7) is arranged outside the upper cover plate (3) and the lower cover plate (4), the piezoelectric stack (2), a Bragg fiber grating temperature sensor (8) and the electrode (6) are arranged in the cavity, and the watertight connector (5) and a watertight socket (10) are arranged on the upper cover plate (3); the piezoelectric stack (2) is a driving structure of the transducer and is formed by stacking piezoelectric single crystal wafers with polarized thicknesses in opposite polarization directions, alternating current is supplied to all the piezoelectric single crystal wafers after the piezoelectric single crystal wafers are connected in parallel, the piezoelectric stack (2) vibrates in a reciprocating mode along the stacking direction, and the electrode (6) is a thin copper sheet and is clamped between the two piezoelectric single crystals and used for communicating silver coatings on the surfaces of the piezoelectric single crystal wafers and a lead.

3. The underwater acoustic transducer capable of measuring temperature online according to claim 1, wherein: the Bragg fiber grating temperature sensor (8) consists of a Bragg fiber grating (11), a protective shell (12), an adapter tube (13), a fiber sheath (14) and an optical fiber (22), the fiber sheath (14) and the optical fiber (22) form a test fiber (9), and the adapter tube (13) is connected with the protective shell (12) and the fiber sheath (14); the Bragg fiber grating (11) is positioned in the protective shell (12), and the protective shell (12) is in close contact with the surface to be measured; one end of the protective shell (12) is closed, the other end of the protective shell leads out the test optical fiber (9), and the Bragg optical fiber grating (11) is in a stress free state in the protective shell (12).

4. The underwater acoustic transducer capable of measuring temperature online according to claim 1, 2 or 3, wherein: the Bragg fiber grating temperature sensor (8) is fixed on the surface to be measured in the transducer through bonding, clamping or embedding.

5. The underwater acoustic transducer capable of measuring temperature online according to claim 3, wherein: the protective shell (12) is made of hard materials with good heat-conducting property of iron and copper.

6. The underwater acoustic transducer capable of measuring temperature online according to claim 1 or 2, wherein: the watertight socket (10) consists of a metal round pipe (17), a protection pipe (19) and a groove (20), a fixing platform (18) is arranged at the middle section of the outside of the watertight socket (1)), and the fixing platform (18) is arranged between the upper cover plate (3) and the watertight sealing layer (7) and is used for fixing the installation depth of the watertight socket and bearing the water pressure borne by the watertight socket; one end of the watertight socket (10) facing the outside of the transducer is provided with a protection tube (19) connected with a metal round tube (17), the metal round tube (17) penetrates through the test optical fiber (9) and then is plugged by hard waterproof glue, and an O-shaped sealing ring is mounted on the groove (20) and used for sealing the upper cover plate (3) and the watertight socket (10).

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