CN205748623U - Microbubble generation electrode and device and the measurement apparatus of bubble resonance frequency - Google Patents

Abstract

The invention relates to a micro-bubble generating electrode and a device and a measuring device for the resonant frequency of bubbles, belonging to the field of underwater acoustics. A DC voltage is applied to both ends of the conductive rod to generate and Bubbles form bubble groups. According to the requirements of the bubble concentration, the number of conductive rods or the discharge method are reasonably designed. The bubbles are approximately normally distributed in the water medium. According to the sound wave propagating in water, its emission frequency is the same as the bubble resonance frequency The principle of the largest sound wave attenuation is to use the hydrophone to make a difference to the sound wave amplitude received under the condition of the presence or absence of bubbles, and the amplitude difference is the largest or a relatively large difference frequency point or range within a certain range of the largest value, and then The resonant frequency range of the bubbles is obtained, and the design of the simple bubble generating device and the resonant frequency device in the pool are completed accordingly. The device for generating bubbles by electrolyzing water is simplified, and the device for measuring the resonant frequency of bubbles is simplified.

Description

Electrode and device for generating microbubbles and measuring device for bubble resonance frequency

technical field

The invention relates to the field of underwater acoustics, in particular to the field of measurement of the resonant frequency of micro-bubbles.

Background technique

The strong dispersion and strong nonlinear acoustic characteristics of sparkling water have always been a topic of interest to people. As we all know, if there are bubbles in the liquid, the acoustic impedance and sound compression characteristics of air and liquid are significantly different, which often leads to the acoustic characteristics of the medium. Changes occur, that is, when sound waves propagate in a liquid containing bubbles, the forced vibration of the bubbles will cause strong sound attenuation and dispersion, and due to the nonlinearity of vibration, the secondary waves generated by the bubbles not only contain fundamental wave components, But also contains advanced harmonics. Bubble resonance will lead to the strongest acoustic nonlinearity. In the field of underwater acoustics, it has been studied to improve the emission efficiency of the acoustic parametric array. It is also used to detect the existence and size of bubbles in engineering.

When the bubbles in the bubble-containing liquid have a certain distribution, different sizes of bubbles have different effects on nonlinear effects, and only the bubbles that resonate with the frequency doubling of the sound wave play a major role. Therefore, only the bubbles with the size of resonance bubbles are the main contributors to the nonlinear parameters of the bubble-containing liquid at different concentrations. Therefore, in order to use the specific increase of the nonlinear parameters of the water medium under the condition of the presence of air bubbles, it is necessary to measure its resonant frequency. In 1992, Wu and Zhu reported the work on nonlinear acoustic parameters in water containing stable and uniformly sized bubbles, and showed that the number of bubbles in water varies with the equilibrium radius approximately as a Gaussian distribution. Bubbles in the water medium can change its acoustic properties. Bubbles have strong dissipation and absorption properties for sound waves propagating in the medium, and can also enhance the nonlinear parameters of the water medium. The resonant frequency band range of the bubble is also a very concerned parameter for underwater acoustic measurement. Therefore, it is a very important step to measure the resonant frequency of the bubble emitted by the bubble generator. When the frequency of the bubble is consistent with the frequency of the emitted sound wave, the sound wave resonates, At this time, the degree of sound attenuation is the largest, so the resonant frequency of the bubble can be found accordingly, and then the sound emission frequency of the bubble can be obtained.

Contents of the invention

The technical problem to be solved by the present invention is to provide a micro-bubble generating electrode and device and a device for measuring the resonant frequency of the bubbles, simplify the device for electrolyzing water to generate bubbles, and simplify the device for measuring the resonant frequency of the bubbles.

In order to solve the above problems, the present invention provides a micro-bubble generating electrode: the micro-bubble generating electrode includes: 2n conductive rods, a power interface and an insulating plate, the 2n conductive rods are fixed on the insulating plate, and the 2n conductive rods pass through The power supply interface is connected to the positive and negative poles of the power supply alternately, and every two adjacent conductive rods form a group of conductive loops, where n is a positive integer.

In order to solve the above problems, the present invention also provides a micro-bubble generating device: the device includes a micro-bubble generating electrode, a generating pool and a DC power supply, and the micro-bubble generating electrode is arranged at the center of the bottom of the generating pool; the DC power supply The power supply electrode of the microbubble generation electrode is connected to the power supply interface.

In order to solve the above problems, the present invention also provides a measuring device for the resonance frequency of microbubbles: the device includes a microbubble generating device, a sound emitting source, a hydrophone and a data collector; the sound emitting source and the hydrophone The distance from the bottom of the generating pool of the microbubble generating device is equal, and the signal output end of the hydrophone is connected with the signal input end of the data collector.

By adopting the device of the invention, the design of the simple bubble generating device in the water pool and the measurement of the resonant frequency can be completed. Depending on the actual application of the bubble concentration, the external power supply voltage can be used to adjust, and the bubble concentration can also be changed by increasing or decreasing the number of conductive rods or the discharge method. The device and method are simple and easy to operate.

In the electrode of the present invention, the 2n conductive rods are of equal length and arranged at equal intervals.

The emission sound source described in the measuring device of the present invention comprises a signal source and a emission transducer, and the signal output end of the signal source is connected with the signal input end of the emission transducer; the distance between the emission transducer and the hydrophone The bottoms of the generating pools of the micro-bubble generating device are at equal distances.

The measurement device of the present invention also includes a power amplifier and a measurement amplifier, the power amplifier is electrically connected between the signal source and the transmitting transducer; the measurement amplifier is electrically connected between the hydrophone and the data collector.

The measuring device of the present invention further includes a signal analyzer, the signal input end of the signal analyzer is respectively connected with the signal output end of the signal source and the signal output end of the hydrophone. The measuring device of the present invention further includes a computer, and the signal input end of the computer is connected with the signal output end of the data collector.

Description of drawings

Fig. 1 is the structure diagram of microbubble generating electrode;

Fig. 2 is the structural representation of microbubble generating device;

Fig. 3 is the structural representation of the measuring device of microbubble resonance frequency;

Fig. 4 is the flowchart of the measurement method of microbubble resonance frequency;

Fig. 5 is a curve diagram of measurement results of bubble Xie vibration frequency;

Fig. 6 is the variation curve of signal source sending frequency;

Figure 7 is an electromechanical analogy diagram of small bubbles in liquid under the action of sound waves.

detailed description

In order to make the purpose, technical solution and advantages of the present invention more clear, the embodiments of the present invention will be described in detail below in conjunction with the accompanying drawings. It should be noted that, in the case of no conflict, the embodiments in the present application and the features in the embodiments can be combined arbitrarily with each other.

As shown in Figure 1, the insulating plate 13 in the micro-bubble generation electrode 1 is used for fixing the conductive rod 11. The 2n conductive rods 11 are equal in length, and the conductive rods 11 are fixed on the insulating plate 13 at regular intervals. The rod 11 passes through the insulating plate 13, and the red and blue conductive wires are used as the power interface 12 to connect with the conductive rod 11, and 2n conductive rods 11 are connected to the positive and negative poles of the power supply through the power interface 12 alternately, and are used to supply power to the conductive rod 11 .

Increasing the number of conductive rods 11 or the discharge method and increasing the density of the electric rods can increase the concentration of generated bubbles. In practical applications, it can be reasonably designed and modified according to the requirements of the bubble concentration.

As shown in Fig. 2, the microbubble generating electrode 1 is placed in the center of the generating pool 21, and the principle of generating bubbles is as follows. Using a regulated voltage and current power supply, a DC voltage is added between the positive and negative electrodes of the power interface 12 to generate electricity during the electrolysis of water. and bubble, and The specific gravity is small, with the release of gas, and Gradually float up, thus forming bubble groups with different radii, and then forming a bubble curtain. The bubbles are approximately normally distributed in the water medium. The equation for the electrolysis of water at the electrode is:

The size of the external electrode voltage will affect the concentration of bubbles and the rising rate of bubbles per unit volume. Therefore, the size of the external supply electrode voltage also has a certain degree of influence on the bubble concentration.

The measurement principle of the microbubble resonance frequency is as follows:

According to the principle that sound waves propagate in water, when the emission frequency is the same as the resonant frequency of the bubbles, the sound wave attenuation is the largest, use the hydrophone 4 to make a difference between the received sound wave amplitudes under the condition of whether there are bubbles, and find the maximum amplitude difference Or a relatively large difference frequency point or range within a certain maximum range, and then obtain the resonant frequency range of the bubbles, because the bubbles are approximately normally distributed in the water medium, the resonant frequency of the bubbles can be calculated statistically for the bubble group mean radius.

As shown in Figure 4, the method for measuring the resonant frequency of the micro-bubbles uses the method of receiving the acoustic signal amplitude difference to find the resonant frequency of the bubbles.

(1) The signal source 31 sends a pulse signal with continuous frequency modulation, and uses the transmitting transducer 32 to transmit a certain frequency at intervals of a certain bandwidth △ f . The frequency of the first sound wave emission is f , and the frequency of the second sound wave emission is f + △ f , the frequency of the third emitted sound wave is f + 2△ f ..., the frequency of the Nth emitted sound wave is f + ( N -1)△ f . Utilize the hydrophone 4 to receive at a certain distance from the transmitting transducer 32, after the signal passes through the measuring method amplifier, whether the received signal is analyzed by the signal analyzer 8 is normal, if normal, then utilize the data collector 5 to record the data and pass to The computer 9 respectively reads the amplitude A ₁ displayed on the computer 9 of the first transmitted signal, the received amplitude of the second transmitted signal is A ₂ , and the received amplitude of the third transmitted signal is A ₃ ..., then The received amplitude of the Nth transmitted signal is A _N .

(2) Externally apply a 7V DC power supply 22 to supply power to the conductive rod 11. After seeing that a stable bubble layer is generated in the generation pool 21, the signal source 31 sends a pulse signal with continuous frequency modulation. △ f emits a certain frequency, the frequency of the first sound wave is f , the frequency of the second sound wave is f + △ f, the frequency of the third sound wave is f + 2△ f ..., the Nth sound wave The frequency is f + (N-1)△ f . Utilize the hydrophone 4 to receive at a certain distance from the transmitting transducer 32, after the signal passes through the measuring method amplifier, whether the received signal is analyzed by the signal analyzer 8 is normal, if normal, then utilize the data collector 5 to record the data and pass to The computer 9 respectively reads the amplitude B ₁ displayed on the computer 9 of the first transmitted signal, the received amplitude of the second transmitted signal is B ₂ , and the received amplitude of the third transmitted signal is B ₃ ..., then The received amplitude of the Nth transmitted signal is B _N .

(3) Draw the relationship curve between the amplitude of the signal received by the hydrophone 4 and the frequency of the emitted sound wave under the state of (1).

(4) Make the relationship curve between the amplitude of the signal received by the hydrophone 4 and the frequency of the emitted sound wave under the state of (2).

(5) Make a relationship curve between the bubble amplitude difference and the emitted sound wave frequency under the condition of having or not having bubbles.

(6) From the curve made in (5), find the frequency point where the amplitude decreases to the maximum value, and this point is the resonant frequency of the bubble.

The sound attenuation of bubble-containing water, especially when bubbles resonate, is much larger than that of pure water, so the present invention can directly obtain the resonance frequency of bubbles based on this principle.

Example

The device provided by the invention is applied to measure the resonant frequency of the microbubbles produced by the water medium, specifically as follows:

The micro-bubble generating electrode 1, the conductive rod 11 is a stainless steel conductive rod, the diameter of the conductive rod 11 is 8mm, 2n conductive rods 11 are equal in length, and the length is 1 meter, and the insulating plate 13 is rectangular and 0.5m long , 2n conductive rods 11 pass through the insulating board 13 at intervals of 2 cm, leaving a length of 10 cm on the other side of the insulating board 13. 11 is fixed, and the conductive rod 11 is connected with the red and blue conductive wires as the power interface 12, which is used to supply power to the conductive rod 11.

The microbubble generating device 2, the generating pool 21 is a 4m*3m*2m muffler pool, and the DC power supply 22 adopts a DH 1718 dual-channel tracking stabilized voltage and stabilized power supply.

As shown in Figure 3, the instrument used for measuring the bubble resonance frequency: a 2-channel Tek 3102 signal source 31, which is used to provide a signal to the transmitting transducer 32; a B&K2713 power amplifier 6, which is used to output the signal Power amplification; a standard hydrophone B&K8101, with a receiving directivity of 183dB, used to receive underwater acoustic signals; a B&K2636 measurement amplifier 7, used to amplify the received acoustic signal in voltage; a Tek 4034 signal analyzer 8. It is used to detect the transmitted signal and received signal to see if the signal is normal; a multi-channel PULSE data collector 5 is used to collect the signal received by the hydrophone 4; a computer 9 is used to monitor the time domain waveform , the waveform is normal, that is, the experimental data is stored in the hard disk of the computer 9 .

Measurement of the resonant frequency of the bubbles: put the electrolyzed water electrode into the bottom of the generating pool 21, place it between the transmitting transducer 32 and the B&K8101 receiving hydrophone 4, observe the change of the sound amplitude after the sound wave passes through the bubble layer, and find the resonant frequency point. Before the test, ensure that the acoustic center of the transmitting transducer 32 and the receiving hydrophone 4 is on the same straight line, the distance between the transmitting transducer 32 and the receiving hydrophone 4 is 186cm, and the water entry depth of the receiving hydrophone 4 is 52cm. 18cm away from the bottom of the pool, the distance between the microbubble generating electrode 1 and the transmitting transducer 32 is 138cm, and the distance between the transmitting transducer 32 and the pool wall is 18cm. During the test, the transmitting signal is a CW pulse. As shown in Figure 6, the pulse period is 100ms, the pulse filling number of 35kHz signal is 50, the measurement amplifier 7 is adjusted to an appropriate multiple, and the Pulse is used for data acquisition. Assuming that the test environment is an isotropic free sound field, the sound wave expands spherically in the pool.

In order to correctly distinguish the direct sound and the reflected sound reaching the hydrophone 4, and accurately process the experimental data, the signal source 31 is used as the external trigger source of the data collector 5Pulse to ensure that the first signal collected by the Pulse is is the direct sound, thus distinguishing the direct signal from the reflected signal.

Carry out the attenuation control test when there are no bubbles and bubbles. A continuous single-frequency signal is emitted, the signal frequency changes every 10kHz from 10kHz to 80kHz, and the peak-to-peak amplitude of the signal source 31 is set to 800mV. The power amplifier 6 is rotated to 60dB, and the measurement amplifier 7 is adjusted to an appropriate multiple for PULSE acquisition. The data length is 120s when there is no bubble, and the data length is 300s when there is a bubble. The power statistics of each frequency signal without bubbles and with bubbles are shown in Table 1.

The sound attenuation curve of electrolytic bubbles is shown in Figure 5.

Bubbles are generally dispersed by gas entering the liquid layer through small holes. Small bubbles do not belong to sound-absorbing materials. When there are small bubble groups in water, there will be obvious absorption and scattering effects. After the sound wave passes through such small bubble groups, it will produce a lot large attenuation. The small bubble is similar to the resonant cavity, and it deforms uniformly under the action of sound waves. It is equivalent to an elastic element. The electromechanical analogy diagram is shown in Figure 7.

Equivalent modulus of elasticity: , the radiation acoustic resistance: , the resonance mass: , the total pressure acting on the small bubble: . in, is the bubble radius; is the acoustic angular frequency; is the beam; is the speed of sound in the medium; is the medium density; is the bubble surface area; is the pressure acting on the bubble; is the ratio of specific heat of gas at constant pressure to specific heat at constant volume. For air under standard conditions, , is the small bubble volume. From the electromechanical analog circuit, the relationship between the equivalent mechanical impedance and the resonant frequency of the small bubble when the small bubble is forced to vibrate is obtained:

is the bubble radius, is the original frequency of the sound wave, is the wave number, is the speed of sound in the medium, is the medium density, is the pressure acting on the bubble, is the ratio of isobaric specific heat to isovolumetric specific heat of gas, is the bubble surface area.

For bubbles in water, take , air , and assuming that the bubble is near the water surface, then is 1 standard atmosphere, thus: ,in, The unit is cm. After obtaining the resonant frequency of the bubble, the radius of the bubble can also be obtained through this formula.

The present invention can also have other multiple embodiments, without departing from the spirit and essence of the present invention, those skilled in the art can make various corresponding changes and deformations according to the present invention, these corresponding changes and All deformations should belong to the protection scope of the appended claims of the present invention.

Claims (8)

1. A micro-bubble generating electrode, characterized in that the micro-bubble generating electrode comprises: 2n conductive rods (11), a power interface (12) and an insulating plate (13), and the 2n conductive rods (11) are fixed on On the insulating plate (13), 2n conductive rods (11) are connected to the positive and negative poles of the power supply through the power interface (12) alternately, and every two adjacent conductive rods (11) form a group of conductive circuits, where n is a positive integer. 2 . The electrode according to claim 1 , characterized in that, the 2n conductive rods ( 11 ) are arranged with equal lengths and equal intervals. 3. A microbubble generating device, characterized in that the device comprises the microbubble generating electrode (1), a generating pool (21) and a DC power supply (22) according to claim 1, and the microbubble generating electrode ( 1) Set at the center of the bottom of the generating pool (21); the power electrode of the DC power supply (22) is connected to the power interface (12) of the microbubble generating electrode (1). 4. A device for measuring the resonance frequency of microbubbles, characterized in that the device comprises the microbubble generating device (2) according to claim 3, a sound emitting source (3), a hydrophone (4) and a data collector (5); the emission sound source (3) and the hydrophone (4) are at the same distance from the bottom of the generating pool (21) of the microbubble generating device (2), and the signal output terminal of the hydrophone (4) is connected to the The signal input terminals of the data collector (5) are connected together. 5. The measuring device according to claim 4, characterized in that, the emitting sound source (3) includes a signal source (31) and a emitting transducer (32), and the signal output terminal of the signal source (31) Connected to the signal input end of the transmitting transducer (32); the transmitting transducer (32) and the hydrophone (4) are at the same distance from the bottom of the generating pool (21) of the microbubble generating device (2) . 6. The measuring device according to claim 5, characterized in that, the measuring device further comprises a power amplifier (6) and a measuring amplifier (7), and the power amplifier (6) is electrically connected between the signal source (31) and between the transmitting transducers (32); the measuring amplifier (7) is electrically connected between the hydrophone (4) and the data collector (5). 7. The measuring device according to claim 5 or 6, characterized in that the measuring device further comprises a signal analyzer (8), the signal input terminal of the signal analyzer (8) is connected with the signal of the signal source (31) respectively The output end is connected with the signal output end of the hydrophone (4). 8. The measuring device according to claim 7, characterized in that the measuring device further comprises a computer (9), and the signal input end of the computer (9) is connected to the signal output end of the data collector (5) .