Hydrodynamic Cavitation, Acoustic Characteristics And Experimental Research

The water is the source of life, and the water which is suitable for humanity enjoys is only 0.01% of Earth's water total resources. Humanity's production and everyday life have caused pollution to the water. The water pollution has caused the precious water resources which humanity can use to decrease little by little, and harmed humanity's health. The World Health Organization's investigation indicated that, 80% of the human disease concerns with the water. The traditional water treatment method has already could not satisfied the new environmental protection request. How to degrade the pollutant in water effectively and more rapidly then becomes a stern question. The cavitation technology is one kind of new technology to degrade water. In recent years, the scholar has paid attention to the ultrasonic cavitation and the hydrodynamic cavitation for the water degradation. But the ultrasonic cavitation can only be carried on the experiment in the low-power vessel, and has difficulty to enlarge the capacity and to be carried on scale processing. The structure of the hydrodynamics generator is simple and durable; the process load is big; the power consumption is small as well as its power supply convenient. It thus suits in the industry apply. This article mainly discusses the acoustics characteristic and effectiveness of hydrodynamic cavitation induced by perforation plate. The primary content and the conclusion are as follows.(1) The hydrophone is used to carry on the survey to cavitation noise spectrum. The result obtained is that different perforation plate caused different noise spectrum when cavitation occurred. The noise spectrum which the identical aperture perforation plate produces has certain similarity. When the pressure intensity is enlarged, the phenomenon is obtains that the prominent peak bunch of noise spectrum induced by multi-aperture perforation plate shift to the high frequency direction. The noise spectrum induced by single aperture perforation plate has the approximate line spectrum ingredient. The single aperture perforation plate is easy to produce whistling.The theory computation and the ANSYS simulation of the vibration of the perforation plate have been performed to study the relation of the vibration frequency and the cavitation noise spectrum obtained. Under the specific condition, the noise spectrum obtained presents the obvious line spectrum distribution and has ultrasonic ingredient. In that situation, the high-velocity flow impacted perforation plate and caused the perforation plate to vibrate intensely and to send out ultrasonic. The noise spectrum produced by the perforation plate cavitation and the eddy whistle cavitation has certain similarity. When the fierce vibration produces ultrasonic, the perforation plate is stimulated, and then the noise spectrum produced by the perforation plate cavitation and the reed whistle cavitation and the piezoelectricity ultrasonic transducer cavitation has certain similarity. (2) The hydrodynamic cavitation experiment has been carried on, and the different parameters which influence cavitation effect such as time, aperture, factor of porosity, import intensity of pressure have been studied. Other studies have been carried out simultaneously in the experimental process to find other factors which affect the cavitation effect, for example the cavitation produced by pump in the high speed rotation condition and the cavitation produced by valve and so on. The result indicated that the degradation effect of Rhodamine B by different perforation tablet is different, and under the low inlet intensity of pressure the cavitation effect is good, and degradation rate increases along with the time extension, and the relation of the inlet intensity of pressure and the degradation change is complex. The length of cavitation region has very tremendous influence to the cavitation effect, and the length must enough long to be able to produce very good cavitation effect. In the application, if the intensity of pressure request can be satisfied, the aperture number of the perforation plate should be as big as possible, in order to obtain the best cavitation effect. The pump and the valve cavitation have the influence to the total cavitation effect.(3) The union of the ultrasonic cavitation and the hydrodynamic cavitation has been carried on, and the mutual function effect has been studied. The order of the occurrence of the two kinds of cavitation has been changed, and the influence of the change to the union effect has been analyzed. The result discovered is that, under the experimental condition, the ultrasonic cavitation and the hydrodynamic cavitation have the very strong mutual inhibitory action, and the ultrasonic cavitation enables the hydrodynamic cavitation to occur, and the high-pressured condition of the hydrodynamic cavitation also causes the ultrasonic cavitation effect unsatisfactory.(4) The cavitation enhancement method has been discussed. The air had been embedding in the liquid before cavitation occurred, and the influence of the flux of the air to the hydrodynamic cavitation has been studied. The result indicated that, embedding air in the liquid was able to promote the hydrodynamic cavitation, but the flux of the air has a best value, because oversized flux can suppress the hydrodynamic cavitation. The water degenerate function of ozone and the union of the ozone and the hydrodynamic cavitation have been carried on to study the effect of the total degradation effect. The research finds the ozone has the very strong degradation function to the pollutant. If the quantity of ozone used is higher, the degrading rate is higher. The hydrodynamic cavitation can enhance the degradation effect of ozone greatly and reduce the use of ozone. The union of the ozone and the hydrodynamic cavitation is one kind of water treatment way which doesn't bring pollution themselves and has the very good application prospect.