High Strength Sound Field Characteristics And Measurement Methods

Since the emergence of cavitation phenomenon, it has been widespread concern. On the application of ultrasonic cavitation is become more common, such as: ultrasonic cleaning, ultrasonic emulsification, ultrasound therapy and the use of ultrasound to accelerate chemical reactions or enhance the chemical yields, etc. These applications are mainly use of the high temperature, high pressure, and the knock-on effection of microfluidics when cavitation generated. Study on the cavitation phenomenon began in the late nineteenth century and has attracted a large number of outstanding acoustics expert input to the research in this area. However, theoretical study of ultrasonic cavitation and the complexity of the cavitation sound field leading to the research of cavitation mechanism behind the practical application. So, there is the lack of theoretical guidance and norms in the actual industrial production.High-power cavitation sound field (high-strength sound field) is the complex field that is the steady-state signal of plus ultrasound superimposes the nonstationary signals of "steady-state cavitation" and "transient cavitation". So, it is an extremely important practical significance for study this field's characteristics and measurement method.In this paper, theoretical, experimental and signal processing were used to study high-strength sound field's characteristics and measurement method. The main work and relevant conclusions are as follows:(1) It is a more ideal choice that uses piezoelectric hydrophone to measure the cavitative sound field, behind compare with a variety of sound field measurement method for practicality, authenticity and validity.(2) At different input power conditions, the high-strength field of rod ultrasonic transducer were analyzed by spectrum, some useful patterns were got. As the input power increases, the rate fundamental decrease after increased to an extreme value, but after that has emerged other increasing and decreasing trends; Half sub-harmonic amplitude increased gradually to a certain value began to decline; Half sub-harmonic, high harmonics and harmonics can be clearly seen that indicating the rod ultrasonic transducer has shown a significant cavitation phenomenon when it work; Input electric power increased from 900 watts to 1000 watts, the fundamental, sub-harmonic, second harmonic, third harmonic and the first high-order harmonic are decrease. The above features indicate that as the power increases, the cavitation in liquid has not always increase but there would be a great value.(3) In different input power conditions, the rod transducer's sound field is analyzed by inverted spectrum. Got some rules can not be observed in the frequency spectrum: there are some line spectrums that have a certain relationship with the fundamental frequency. They may provide some useful information for the characteristics of cavitation field.(4) Based on the engineering application, an evaluation method for the sound field intensity is advanced. It can be found that they have a better consistency when this method compare with aluminum foil etching method.(5) In different conditions, the high-strength field was measured by hydrophone. We can conclude that sound-field intensity is not with the input electric power and liquid temperature increases have been increasing, but there is an optimum value. And the possible explanation for this phenomenon is made.(6) The pressure signals were decomposed by wavelet transform. We can see that the energy of d4 layer contains the fundamental frequency in the entire frequency range accounts for the main components; the signal of high-strength field is modulated by the frequency of 75Hz. Moreover, the cavitation coefficient that can describe the strength of cavitation is definitude. It has a good consistency with the theoretical maximum sound pressure.