Study On Characteristics And Measurement Methods Of The High-power Low-frequency Ultrasonic Fields For Cleaning

As for the application of ultrasonic process technology, ultrasonic cleaning is one of the most extensive application, and it has many advantages, such as fast cleaning rate, good cleaning quality, low cost and apt to realize automatization, etc. Cavitation is the most distinct characteristic of the high-power low-frequency ultrasonic fields, and it is also regarded as the primary mechanism of ultrasonic cleaning. Nevertheless, the measurement question of the high-power low-frequency ultrasonic fields hasn't been resolved well, because of the incomplete cavitation theory and the complexity of cavitation fields. The universal acceptant standard measurement hasn't been found up to the present so that it is difficult to judge of the performance of ultrasonic cleaning machines scientifically. However, it is important to measure the cavitation fields so far as the scientific research and judging of the performance of ultrasonic vibration systems and ultrasonic process effect, so to present the repeatable method is urgent affairs through basic and applied research on ultrasonic cleaning. In this paper, the characteristics and measurement methods of the high-power low-frequency ultrasonic fields for cleaning is studied by means of experiment research mainly, in order to present the more quantitative and more practicable measurement method of cavitation fields.This paper compares various measurement methods, then chooses the hydrophone as measuring instrument to study the pressure waveforms of the ultrasonic fields for cleaning in time domain. Based on the primary know about the characteristics of ultrasonic fields, the ultrasonic power of single transducer cleaning system is measured and the relation between ultrasonic power and pressures is studied. Moreover, the energy scale method of the probe is proposed from the point of view of energy transfer. In the last part, in order to know the cavitation fields thoroughly, spectrum analysis methods are adopted to study the cavitation fields, and the separate method of cavitation noise spectrum is presented and compared with spectrum level analysis method.(1) Randomicity and periodicity are the characteristics of pressure waveforms of ultrasonic cleaning fields, so to analysis the metrical data needs to apply random signalprocess theory. Moreover, it is necessary to acquire a long time data in order to enhance the results repetition and ensure that the time interval is equal to integral times of the period in order to reduce error.(2) Based on the measurement theory of Watt meter method, the ultrasonic power of single transducer cleaning system is measured and the relation between ultrasonic power and pressures is studied. The experimental results show the cavitation intensity will become lower when the energy input reaches to a certain extent. The result is important for the liquid process of power ultrasonic and indicates that there is the optimal input energy corresponding to the best process effect.(3) A method that can evaluate the high power ultrasonic fields quantitatively and practicably is proposed. This method evaluate ultrasonic fields based on ultrasonic power and scaled the probe by way of the ultrasonic power percent unit area. The method can evaluate the performance of ultrasonic cleaning machines under the same conditions, in addition choose and control the ultrasonic intensity in application to engineering.(4) Power spectrum analysis methods are adopted to study pressure signals of the cavitation fields, and the separate method of cavitation noise spectrum is presented, after compared it with spectrum level analysis method, the results show that the separate method can more directly reflect the cavitation intensity, give the delicate analysis on the transient cavitation and the stable cavitation, and help to know the non-linear process of cavitation fields thoroughly. The method contributes to study the mechanisms of ultrasonic energy action on the substances.