Cavitation is an established method for improving processes in various industries, e.g. treatment of kidney stones in medicine, increasing biogas production and commercially widely used for ultrasonic cleaning of submerged objects. The topic of the master’s thesis derives from previous research to improve the process of wastewater treatment using cavitation. Problems arise as conventional methods for generating cavitation require relatively large amounts of samples for their operation, which cannot always be obtained due to security, financial or other constraints. Therefore, as part of the master’s thesis, a new device was designed for generating hydrodynamic cavitation in samples of small volumes, which are suitable for testing medical, pharmaceutical or biological preparations with a volume of less than 10 ml.
In the following, measurements on the manufactured device and simulation experiments of the electromagnetic model of the device with the Ansys Maxwell software tool are presented.
To begin with, a simulation study of different construction configurations of the device was performed. We found that it makes sense to use field concentrators, as they increase the average force on a permanent magnet by 35 %. A 3-axial teslameter was used to measure the magnetic flux density on the surface of the ferromagnetic core. A comparison with the simulation results shows the deviation of the simulations from the measured values by an average of −18 %. The same measurements on the surface of permanent magnets turn out to be accurate enough for our needs, as the largest deviation of the simulated values from the measured values is by −6, 7 %. Besides, measurements of the force on the permanent magnet along the opening in the core were performed. The measured forces are on average 20 % higher than the simulated ones. By comparing the performed measurements and electromagnetic simulations, it can be concluded that the use of simulations makes sense and the results are accurate enough to further investigate the operation of the device in different configurations of the ferromagnetic core and permanent magnets.
Moreover, with the Ansys Simplorer software tool we tested the operation of various configurations of the power supply and control part of the device. Based on the results, we propose the implementation of a high-voltage power supply system, as this would increase the slope of the current pulse by more than 2 times. We propose three new ways of generating current pulses: current pulse with a tail, trapezoidal current pulse shape and current pulse for force compensation.
In the last part of the master’s thesis, we observed and analysed the events inside the cavitation chamber during operation at different configurations of permanent magnets with a high-speed camera, hydrophone and current probe. A permanent magnet with a central hole and only a slightly smaller outer diameter than the diameter of the cavitation chamber bore proved to be the most optimal configuration of the sub-assembly for generating cavitation. The difference in diameters must allow the magnet to move freely through the hole.
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