A method of monitoring ultrasonic cavitation intensity

Abstract

The application belongs to the technical field of ultrasonic cavitation, and particularly relates to an ultrasonic cavitation intensity monitoring method, which comprises the following steps: 1) inserting an ultrasonic transducer into a liquid to be treated to generate ultrasonic cavitation, and generating cavitation noise during the ultrasonic cavitation; 2) converting vibration signals radiated by the ultrasonic cavitation noise into electric signals, and then filtering and amplifying the electric signals through a signal collector to obtain a time domain signal p(t); 3) performing fast Fourier transform (FFT) on the time domain signal p(t) by a signal processing unit to obtain a frequency domain signal P(f); 4) filtering white noise and environmental noise in the frequency domain signal P(f) to obtain a spectrum P1(f) of the ultrasonic cavitation noise; and 5) using the spectrum of the ultrasonic cavitation noise to integrate sound pressure in the frequency domain to obtain cavitation intensity. The application can monitor the cavitation intensity of ultrasonic waves in real time in a special environment.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of ultrasonic liquid treatment, in particular to an ultrasonic cavitation intensity monitoring method. BACKGROUND

[0002] Ultrasonic cavitation is an important phenomenon of power ultrasound in liquid, which can produce shock waves, micro-jets, local high temperature and high pressure and other extreme physical conditions and derive biochemical effects, so that cavitation is widely used in chemical industry, environment, medical treatment, materials and many other fields. In application, real-time monitoring of cavitation intensity excited by ultrasonic transducer is an important link in related industrial production. SUMMARY

[0003] The purpose of the present application is to provide an ultrasonic cavitation intensity monitoring method, which can monitor the cavitation intensity of ultrasonic in special environment in real time.

[0004] In order to achieve the above purpose, the present application adopts the following technical scheme:

[0005] An ultrasonic cavitation intensity monitoring method, the method comprising the following steps:

[0006] 1) inserting an ultrasonic transducer into a liquid to be treated to produce ultrasonic cavitation, and ultrasonic cavitation is accompanied by cavitation noise;

[0007] 2) converting the vibration signal radiated by the ultrasonic cavitation noise into an electric signal, and then filtering and amplifying the electric signal through a signal collector to obtain a time domain signal p(t);

[0008] 3) performing fast Fourier transform FFT on the time domain signal p(t) by a signal processing unit to obtain a frequency domain signal P(f), wherein the FFT formula is shown in formula (1);

[0009]

[0010] Wherein, N is the time domain sampling length, Δt is the signal sampling interval, n=t / Δt is the time point number, f is the signal frequency, and f s is the signal sampling frequency;

[0011] 4) filtering out the white noise spectrum and environmental noise spectrum in the frequency domain signal P(f) to obtain an ultrasonic cavitation noise spectrum P1(f);

[0012] 5) using the ultrasonic cavitation noise spectrum to integrate the sound pressure in the frequency domain to obtain the cavitation intensity

[0013] Wherein, f0 is the highest frequency of the effective ultrasonic cavitation noise spectrum, which can be predicted by actual working conditions and then input into the cavitation intensity calculation formula as a known quantity.

[0014] Preferably, the ultrasonic transducer comprises a back matching, a first input electrode sheet, a second input electrode sheet, a first output electrode sheet, a second output electrode sheet, a piezoelectric ceramic sheet, a flange, a front matching and a horn;

[0015] The back matching, the first input electrode sheet, the second input electrode sheet, the first output electrode sheet, the second output electrode sheet and the flange are sequentially connected and fixed, and the piezoelectric ceramic sheet is arranged between the first input electrode sheet and the second input electrode sheet, the second input electrode sheet and the first output electrode sheet, the first output electrode sheet and the second output electrode sheet and the second output electrode sheet and the flange respectively.

[0016] The flange, the front matching and the horn are sequentially fixed and connected.

[0017] Preferably, the diameter of the end connected with the front matching of the horn is greater than the diameter of the other end.

[0018] Preferably, a groove is arranged on the flange, and a sealing ring is arranged in the groove.

[0019] Preferably, the signal collector is a general-purpose oscilloscope.

[0020] The application also provides an ultrasonic cavitation intensity monitoring device, which comprises an ultrasonic wave generator, an ultrasonic transducer, a signal collector and a signal processor.

[0021] The ultrasonic wave generator is connected with the ultrasonic transducer, the ultrasonic transducer is connected with the signal collector, and the signal collector is connected with the signal processor.

[0022] In the application, four electrode sheets are arranged on the ultrasonic transducer, two of which are used as the input of the electric signal, and the other two are used as the output of the electric signal; the ultrasonic transducer converts the electric signal input from the electrode sheet into ultrasonic wave, generates the ultrasonic cavitation effect, and converts the cavitation noise of the ultrasonic cavitation effect into the electric signal by the piezoelectric ceramic sheet of the ultrasonic transducer, and then outputs the electric signal to the signal collector from the electrode sheet.

[0023] In the application, the ultrasonic transducer is placed in a special environment (high temperature, high pressure and strong corrosion) requiring cavitation effect to normally work and excite the ultrasonic cavitation; the vibration signal of the ultrasonic cavitation radiation is received by the ultrasonic transducer or other monitoring equipment, converted into the electric signal and output to the signal collector, and the signal collector filters and amplifies the input signal and inputs the signal to the signal processing unit to obtain the ultrasonic cavitation intensity. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 The flow chart of the ultrasonic cavitation intensity monitoring method of the application is shown in the figure;

[0025] Figure 2 The structural schematic diagram of the ultrasonic transducer of the application is shown in the figure;

[0026] Figure 3 Structure diagram of the ultrasonic cavitation intensity monitoring device of the present application;

[0027] Figure 4 Viscosity-temperature curve of heavy oil in embodiment 2 of the present application;

[0028] Figure 5 Time-domain acoustic signals of 4 min, 5 min and 6 min cumulative action time in embodiment 2 of the present application;

[0029] Figure 6 Frequency-domain signal of fast Fourier transform in embodiment 2 of the present application;

[0030] Reference signs:

[0031] 1, rear matching; 2, first input electrode sheet; 3, second input electrode sheet; 4, first output electrode sheet; 5, second output electrode sheet; 6, piezoelectric ceramic sheet; 7, flange; 8, bolt; 9, front matching; 10, top screw; 11, amplitude rod. DETAILED DESCRIPTION

[0032] The present application will be further described in detail with the accompanying drawings and specific embodiments.

[0033] Embodiment 1

[0034] As shown in the above ultrasonic cavitation intensity monitoring method, the steps include: Figure 1

[0035] 1) Connect the power supply, adjust the frequency tuning and tracking of the ultrasonic wave generator, so that the ultrasonic transducer always works in the resonant state, ensures the stable output power, inserts the ultrasonic transducer into the liquid to be processed, generates ultrasonic cavitation, and generates cavitation noise during ultrasonic cavitation;

[0036] 2) Use the ultrasonic transducer to receive the vibration signal of ultrasonic cavitation noise radiation and convert the vibration signal into an electrical signal, and then filter and amplify the signal through a signal collector to obtain the time-domain signal p(t) of cavitation noise;

[0037] 3) The signal processing unit performs fast Fourier transform (FFT) on the time-domain signal p(t) to obtain the frequency-domain signal P(f), wherein the FFT formula is shown in formula (1).

[0038]

[0039] Wherein, N is the time-domain sampling length, Δt is the signal sampling interval, n=t / Δt is the number of time points, f is the signal frequency, f s ​is the signal sampling frequency. e is the natural constant, j is the imaginary unit, both are known constants, which can be directly used.

[0040] 4) Filter out the white noise and environmental noise in the frequency domain signal P(f) to obtain the frequency spectrum P1(f) containing only ultrasonic cavitation noise.

[0041] 5) Use the ultrasonic cavitation noise spectrum to integrate the sound pressure in the frequency domain to obtain the cavitation intensity

[0042] Where f0 is the highest frequency of the effective ultrasonic cavitation noise spectrum, which can be predicted by the actual working condition and input as a known quantity into the formula.

[0043] p(t) represents the sound pressure received by the circuit, which is actually a series of digital signals, where (t) represents the independent variable of the signal as time. The unit of p(t) can be Fort or converted to Pascal. Since the relative change of data is used to judge whether the cavitation is stable during actual operation, the absolute value is not required, so the invention does not specify the unit and value.

[0044] The expression of the signal and the summation formula of FFT are the general expression methods accepted in the industry, and the invention does not need to be specially mentioned.

[0045] As shown in Figure 2 The ultrasonic transducer comprises a rear matching 1, a first input electrode sheet 2, a second input electrode sheet 3, a first output electrode sheet 4, a second output electrode sheet 5, a piezoelectric ceramic sheet 6, a flange 7, a front matching 9 and an amplitude horn 11.

[0046] The rear matching 1, the first input electrode sheet 2, the second input electrode sheet 3, the first output electrode sheet 4, the second output electrode sheet 5 and the flange 7 are sequentially connected and fixed, and the piezoelectric ceramic sheet 6 is arranged between the first input electrode sheet 2 and the second input electrode sheet 3, the second input electrode sheet 3 and the first output electrode sheet 4, the first output electrode sheet 4 and the second output electrode sheet 5, and the second output electrode sheet 5 and the flange 7.

[0047] The flange 7, the front matching 9 and the amplitude horn 11 are sequentially fixedly connected. The flange 7 and the front matching 9 are an integrated structure, and the front matching 9 is fixedly connected with the amplitude horn 11 through the jackscrew 10.

[0048] The diameter of the connecting end of the amplitude horn 1 with the front matching 9 is greater than the diameter of the other end.

[0049] The flange 7 is provided with a groove, and a sealing ring is arranged in the groove.

[0050] In this embodiment, the material of the back matching is stainless steel, and the material of each electrode sheet is copper, and there are four sheets in total, which are connected to the negative and positive output terminals of the ultrasonic generator, and the negative and positive input terminals of the signal collector from top to bottom. The material of the piezoelectric ceramic sheet is PZT8; the flange is used to fix the transducer, and the upper and lower surfaces are grooved to place the O-ring, which plays a sealing and vibration isolation role. The material of the flange is hard aluminum, which is integrally made with the flange. The bolt is used to apply pre-stress to prevent the piezoelectric ceramic sheet from cracking due to excessive tension. The top screw is used to connect the front matching of the transducer and the amplitude rod. The amplitude rod is in direct contact with the medium to be treated, and is used to amplify the displacement amplitude of the transducer output, and locally form a high sound intensity. The material of the amplitude rod is titanium alloy, and the specific material can also be selected according to the physical and chemical properties of the inserted liquid.

[0051] As shown in Figure 3 , an ultrasonic cavitation intensity monitoring device, the monitoring device comprises: an ultrasonic generator, an ultrasonic transducer, a signal collector and a signal processor;

[0052] The ultrasonic generator is connected to the ultrasonic transducer, the ultrasonic transducer is connected to the signal collector, and the signal collector is connected to the signal processor.

[0053] In this embodiment, the ultrasonic generator (with matching box) is a UGD ultrasonic generator manufactured by the Institute of Acoustics, Chinese Academy of Sciences; the signal collector (with internal acquisition circuit) can be completed by using a general-purpose oscilloscope (for example: model ROHDE & SCHWARZ RTM3004); and the signal processing unit adopts a computer.

[0054] Example 2

[0055] The existing heavy oil has a density of 0.94-1.06 g / cm 3 , and its viscosity-temperature curve is shown in Figure 4 . The heavy oil is treated by ultrasonic cavitation, and the specific operation is as follows:

[0056] 1) The electric power of the ultrasonic transducer is set to 50 W, and the heavy oil is treated at room temperature for 3 min, and then the ultrasonic transducer is turned off;

[0057] 2) The heavy oil is cooled to 90°C at room temperature, the ultrasonic transducer is turned on, and the power is maintained at 50 W, and the heavy oil is treated for 1 min;

[0058] 3) Step 2) is repeated twice, and the total treatment time is accumulated to 6 min.

[0059] During the treatment process, the ultrasonic transducer (or hydrophone) shown in Figure 2 is used to receive cavitation noise, and the time domain acoustic signals of the accumulated treatment time of 4 min, 5 min and 6 min are obtained, as shown in Figure 5 . Then, the time domain signals are subjected to FFT to obtain the frequency domain signals as shown inFigure 6 The frequency domain signal is shown. According to the engineering requirements, the signal is filtered again, f0=63 kHz is selected, and integration is performed, so that the cavitation noise intensities of 4 min, 5 min and 6 min are 1.31, 1.60 and 2.30 respectively.

[0060] The contents not described in detail in the present application can adopt the conventional technical knowledge in the art.

[0061] Finally, it should be noted that the above examples are only used to illustrate the technical solutions of the present application and are not limiting. Although the present application has been described in detail with reference to the examples, those skilled in the art should understand that modifications or equivalent replacements of the technical solutions of the present application do not deviate from the spirit and scope of the technical solutions of the present application, and they should be covered in the scope of the claims of the present application.

Claims

1. A method for monitoring ultrasonic cavitation intensity, the method comprising the following steps: 1) Insert the ultrasonic transducer into the liquid to be treated to generate ultrasonic cavitation, which is accompanied by cavitation noise. 2) The vibration signal of ultrasonic cavitation noise radiation is converted into an electrical signal, and then filtered and amplified by a signal acquisition unit to obtain a time-domain signal. p (t); 3) The signal processing unit processes time-domain signals. p ( t Perform a Fast Fourier Transform (FFT) to obtain the frequency domain signal. P ( f ), where the FFT formula is shown in equation (1); (1)； in, N Δ is the time-domain sampling length. t The signal sampling interval, n = t / Δ t For time points, f For signal frequency, f s The signal sampling frequency; 4) Filter out frequency domain signals P ( f The ultrasonic cavitation noise spectrum is obtained by combining the white noise spectrum and the ambient noise spectrum. P 1( f ); 5) The cavitation intensity is obtained by integrating the sound pressure in the frequency domain using the ultrasonic cavitation noise spectrum. ; in f 0 represents the highest frequency in the effective ultrasonic cavitation noise spectrum; The ultrasonic transducer is equipped with four electrode plates, two of which serve as inputs to the electrical signal and the other two as outputs. The ultrasonic transducer converts the electrical signal input from the electrode plates into ultrasonic waves, generating an ultrasonic cavitation effect. The cavitation noise of the ultrasonic cavitation effect is converted into an electrical signal by the piezoelectric ceramic plate of the ultrasonic transducer and output from the electrode plates to the signal acquisition device.

2. The ultrasonic cavitation intensity monitoring method according to claim 1, characterized in that, The ultrasonic transducer includes a rear matching element, a first input electrode plate, a second input electrode plate, a first output electrode plate, a second output electrode plate, a piezoelectric ceramic plate, a flange, a front matching element, and an amplitude transformer. The rear matching, first input electrode plate, second input electrode plate, first output electrode plate, second output electrode plate, and flange are sequentially connected and fixed, and piezoelectric ceramic plates are respectively arranged between the first input electrode plate and second input electrode plate, the second input electrode plate and first output electrode plate, the first output electrode plate and second output electrode plate, and the second output electrode plate and flange. The flange, front matching and amplitude transformer are fixedly connected in sequence.

3. The ultrasonic cavitation intensity monitoring method according to claim 2, characterized in that, The diameter of the amplitude transformer rod at the front matching connection end is larger than the diameter of the other end.

4. The ultrasonic cavitation intensity monitoring method according to claim 2, characterized in that, The flange is provided with a groove, and a sealing ring is provided in the groove.

5. The ultrasonic cavitation intensity monitoring method according to claim 1, characterized in that, The signal acquisition device is a general-purpose oscilloscope.

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