The thesis is devoted to solving problems at creation of ultrasonic cavitation filters with self-cleaning effect for liquid environments, contains theoretical and practical results of filtration process under conditions of ultrasonic cavitation.
Intensive development of technologies with the use of liquids requires constant improvement of the efficiency of technological equipment, which ensures their purification from mechanical and bacterial contamination. To date, a significant number of methods and equipment for cleaning process fluids have been developed, which differ in efficiency and quality of cleaning. Devices that provide liquid filtration must meet certain requirements, including the degree of filtration from mechanical and bacterial contamination; productivity; possibility of restoration of filtering ability; resistance of the filter element to physical or chemical destruction; term or resource of working capacity.
The most common method of filtration is the purification of liquids using a porous partition. However, this type of filter does not meet all of the above requirements. When using porous partitions, a significant pressure drop is created, which leads to a reduction in flow. Over time, contaminants accumulate in the channels of the porous septum, which leads to secondary contamination of the liquid. Therefore, filters with a porous partition need periodic replacement. However, there are filters that use ultrasonic vibrations for cleaning, the intensity of which exceeds the threshold of cavitation. Filtration in the conditions of an ultrasonic field allows to increase time of uninterrupted work of the filtering equipment due to use of the effects accompanying the phenomenon of ultrasonic cavitation.
However, the lack of methods for calculating ultrasonic cavitation filters and dependencies that will determine their rational operational and design parameters and choose the material, make it impossible to create efficient structures based on the process of ultrasonic exposure to the liquid.
The paper presents an analysis of known methods of regeneration of filter element and means of their implementation in the technological processes of mechanical engineering, chemical industry, medicine and agriculture. On the basis of which the specified physical and mathematical models of interaction of particles of pollutant with a filter element at ultrasonic cavitation filtration in which supersonic speeds of movement of particles of pollutants are considered are resulted.
According to the results of a computer study of the growth of a vapor gas bubble in an ultrasonic medium, the velocity of a contaminant particle near the wall of a collapsing cavitation bubble is obtained.
It is determined by mathematical modeling of the impact interaction of dirt particles with the filter partition, the dependence of wear of structural materials over time under the influence of ultrasonic cavitation of surfaces made of fluoroplastic F4 and steel 12X18H10T. It was found that 12X18H10T steel is twice less exposed to cavitation erosion compared to fluoroplastic F4, and, according to the results of an experimental study of the influence of ultrasonic cavitation process parameters on the relative volume loss of structural materials, it was found that the Young's modulus is significantly larger. the effect on the relative loss of volume of structural materials than the duration of the cavitation effect, ie 12X18H10T is a suitable material for use in ultrasonic cavitation filters.
An engineering method for calculating the resonant elements of the filter housing structure and radiator drives is proposed, the application of which takes into account the operating conditions, characteristics of structural materials and the brand of piezoelectric transducers, which together increases the continuous operation of the filter element. Based on the methodology, the design of ultrasonic filters for technological processes of chicory thickening and sunflower oil purification was developed and implemented, which ensured the achievement of an average of 45% increase in the continuous operation time of filter equipment in production.
According to the results of the experimental study, the dependence of excess and vacuum pressure in the cavitation chamber on the intensity of ultrasonic cavitation was determined and it was determined that the maximum intensity of cavitation exposure falls on the pressure range 0.2…0.3 MPa. Rational parameters of the location of the filter partition relative to the ultrasonic wave in the cavitation chamber are experimentally determined.
