Standing Wave Of Liquid Cavitation Characteristics Of Experimental Research

In recent years, with the application of acoustic cavitation is expanding, the research of acoustic cavitation is became a focus of the domestic and foreigh experts. Because of the complexity of cavitation fields and incomplete cavitation theory, the measurement of cavitation has not been resolved and the method to accurately describe cavitation has not been found. This causes it is difficult to judge and make use of cavitation. Therefore, the accurate measurement of cavitation and quantitative of the characteristic parameters of cavitation is an urgent subject. In this paper, the cavitation noise in the cylindrical reactor is measured based on experimental methodology, and the size and quantity distribution of cavitation bubbles were preliminary studied, in order to make more particularly understand the characteristics of cavitation field.In this paper, spectrum analysis methods are adopted to study the cavitation fields, then chooses the hydrophone and sprctrum analyzer as measuring instrument to measure the cavitation noise of the cylindrical reactor in the distilled water, normal water and 20% salt solution, and according to the information of cavitation noise sprctrum, the size and quantity distribution of cavitation bubbles are estimated. By the massive experimental study, the main results are followed:(1) In the experiment, firstly find a kind of particles to describe the standing wave field, and the motion behaviour of particles is analysed. In the standing wave field, with the combined action of radition pressure and acoustic streaming, the tiny particles are gathered in the pressure loop. Constrast the movement of tiny particles, we know the cavitation bubbles are gathered by the effect of radition pressure and acoustic streaming, and the cavitation bubbles which smaller than the resonant radius are gathered in pressure loop, and the cavitation bubbles which larger than the resonant radius are gathered in pressure node.(2) The spectrum analysis method are adopted to study cavitation noise of the distilled water, normal water and 20% salt solution, the results followed:the rule of cavitation noise spectrum in distilled water is similar to the normal water, with the increase of input electric power, the sound pressure, corresponding each spectrum line, that variation trend is presented increased firstly and decreased then, this indicated that cavitation is not continuously larger with the increase of input electric power, and there is an optimal input electric power exist. The cavitation noise spectrum in 20% salt solution showed that:when the input electric power is 10W, the spectrum line was increased obviously; when the input electric power is 20W, the ultraharmonic are appeared, the cavitation characteristics in 20% salt solution is obvious difference from distilled water and normal water. In addition, form the analysis cavitation noise spectrum in three different liquid, the cavitation field in distilled water has the most stability, the normal water is second, and the 20% salt water is third.(3) Separated the cavitation noise spectrum by the statistical method, the curve of fundamental wave sound pressure level with the change of input electric power showed that:in the three different liquid, the cavitation threshold of the pressure node is less than the value of the pressure loop, which indicated cavitation is easier occurred in pressure node than pressure loop. The curve of relative harmonic sound pressure level, relative subharmonic sound pressure level, relative non-linear sound pressure level with the change of input electric power showed that:in the same input electric power circumstances, the cavitation intensity in 20% salt solution is the strongest in three different liquid, the normal water is second, and the distilled water is third.(4) Take the distilled water for example, based on cavitation noise spectrum of pressure node and pressure loop, the size and quantity of the oscillating bubbles are calculated by statistical method. The results show that:take no account of different plane, the mean radius of all points cavitation bubbles are calculated and its rang is 90μm-150μm, the cavitation bubbles which mean radius is 130μm occupied the major proportion, which objectively reflect the energy characteristics of sound field. The distribution of the quantity of cavitation bubbles obviously depends on the sound field intensity, the total of cavitation bubbles is inequable in different plane, and the total number of cavitation bubbles in pressure node is more than pressure loop, which indicated cavitation is easier occurred in pressure node than pressure loop. Based on the information that reflected by the cavitation noise spectrum, the size and quantity of cavitation bubbles are studied. In this way, we can close to the cavitation bubbles which we need, indentify the high-density of the cavitation bubbles, and finally provide standard for the measurement of sonochemical reactors.