3D Reconstruction And Optimization Research Of Ultrasonic Cavitation Field Based On Spectrum Analysis Method

Since cavitation is the main force accelerating chemical reactions and thatsonochemical reactor is the place where chemical reactions were realized, theintensity and distribution of cavitation field in it is directly related to thesonochemical yield. The measurement and characterization of cavitation field is notonly the guidance for sonochemical reaction to achieve the best effect, but also animportant index to evaluate and optimize sonochemical reaction equipment. In thisstudy, a hydrophone was used to measure the sound field in a cleaning tank. Themeasurement results were further processed in MATLAB software for spectralanalysis, and after the energy separation step3D distribution of cavitation field couldbe got through a graphical user interface (GUI) programmed and packaged byourselves. This method makes the measurement results more visible, making up forthe defect of hydrophone method that the results are not intuitive. Based on thismethod, the cavitation field distribution in the cleaning tank was measured andpresented.There are a lot of factors that influence ultrasonic cavitation. In order to optimizethe cavitation field in the cleaning tank under the given conditions, we studied theinfluence of frequency, power, water level and air content of the medium oncavitation intensity and distribution. Results indicate that: The intensity of cavitationis higher under low frequency, with higher cleaning/reaction strength, but theuniformity of its distribution is worse. While under high frequency, the uniformity ofcavitation distribution is better, with larger cleaning/reaction space, but the cavitationintensity is lower. In the adjustable range of device, the influence of power oncavitation effect is not as good as other factors. The cavitation intensity anddistribution uniformity increase with power in the range of40W~70W. When thepower reaches70W, cavitation intensity almost stays the same along with the increaseof power, and the distribution uniformity even become worse. The water depthinfluences the cavitation field significantly, and there are some resonance depths (thedistance from the bottom is integer times of a quarter wavelength) at which thecavitation intensity and uniformity are both well. Due to the negative effects ofgaseous cavitation, the gas component in the medium would weaken the cavitation effect, so the degassing treatment is very useful to improve the cavitation effect.Detailed study on the influence of gas content on ultrasonic cavitation indicates thatreducing the gas content of medium has a great role in promoting the cavitationintensity and uniformity, but when the oxygen content is lower than a certain value(4.32mg/L for water), continue to reduce the gas content would cause the cavitationeffect decreased slightly on the contrary.In conclusion, in the application process of this cleaning tank, the cavitationeffect is great both in intensity and distribution uniformity when the ultrasonic poweris in the range of60~80W, the medium level stays at a resonant tank liquid level, andthe medium oxygen content falls between3.17~5.02mg/L. For the selection offrequency it is better to make the choice according to the focus of a reaction orcleaning process considering the different requirements of cavitation intensity andhomogeneity. The results of this experiment have an important guiding significancefor the improving of ultrasonic cleaning or sound chemical reaction efficiency.