Development of Ultrasonic Cylindrical Cells for Trapping of Oil Droplets

摘要

This work describes the development of ultrasonic cylindrical cells in the frequency range between 20 and 60 kHz for trapping of oil droplets in water. Each cell consists of a Langevin-type ultrasonic transducer and a cylindrical glass tube. The dimensions of each cell are determined by conducting simulations with the Finite Element Method (FEM). After determine the optimal dimensions, the cells were fabricated, and the pressure field predicted by the FEM were compared with that obtained experimentally by using a hydrophone (8103, Bruel & Kjaer). The comparison between both results shows good agreement when the transducer is excited with a low voltage signal. When the excitation voltage is increased, acoustic cavitation occurs and the signal measured by the hydrophone has many harmonics of the fundamental frequency, which are associated with the nonlinear radial oscillations of air microbubbles.