Realization of cavitation fields based on the acoustic resonance modes in an immersion-type sonochemical reactor

Abstract

Different modes of cavitation zones in an immersion-type sonochemical reactor have been realized based on the concept of acoustic resonance fields. The reactor contains three main components, namely a Langevin-type piezoelectric transducer (20 kHz), a metal horn, and a circular cylindrical sonicated cell filled with tap water. In order to diminish the generation of cavitation bubbles near the horn-tip, an enlarged cone-shaped horn is designed to reduce the ultrasonic intensity at the irradiating surface and to get better distribution of energy in the sonicated cell. It is demonstrated both numerically and experimentally that the cell geometry and the horn position have prominent effects on the pressure distribution of the ultrasound in the cell. With appropriate choices of these parameters, the whole reactor works at a resonant state. Several acoustic resonance modes observed in the simulation are realized experimentally to generate a large volume of cavitation zones using a very low ultrasonic power.

Hydrogen production by water photo-sonolysis: a modal approach to enhance the ultrasonic acoustic field in the solution

“…Those differences were attribute to the influence of cavitation bubbles layers, whose acoustic scattering on the US waves can attenuate or delate the influence of the symmetrical modal response of the solution cylinder in the vessel. This confirms the results from other works in literature [7][8][9] and verify the attenuation of the influence of the geometry of the vessel on the sound pressure field during cavitation on the vessel. Furthermore, measuring the acoustic pressure at different distances from the bottom of the vessel in significant point in the section plan, the position closer to the US source (R) reported the higher values, confirming the relationship between cavitation and distance from the source in the section plan.…”

“…It is not true that the highest values are at the closer positions to the US source, and the apex is reported at 30 mm of distance. The trend of the measurements may suggest the presence of cavitation multilayers (as reported in literature [7][8]).…”

“…Recent advancements in acoustic design include computational modeling and simulation techniques, such as finite element analysis and computational fluid dynamics, to characterize and optimize the cavitation field from the geometry of the reactor. Investigations on the acoustic resonance modes of sonoreactor was performed by Wang [8] comparing cavitations bubbling positions in a water solution into a cylindrical vessel subjected to 20 kHz US by a horn-type 1000 W transducer to computational results of a COMSOL FEM model of the experimental set-up. Resonance frequencies between experiment and simulation diverge of 0.4 kHz (19.4 kHz vs 19.8 kHz), and results comparison achieved a satisfactory comparability in half side of the transversal section.…”

Dynamic resonant frequency control of ultrasonic transducer for stabilizing resonant state in wide frequency band

“…In general, ultrasonic transducers are operated at their resonant frequency for efficient driving as in ultrasonic motors, [1][2][3] sonochemical cavitation, [4][5][6] ultrasonic levitation, [7][8][9][10] wire bonding, 11,12) ultrasonic pumping, [13][14][15] and machining. 16,17) In general, the driving frequency traces a transducer's resonant frequency using a self-oscillator circuit.…”

Understanding the ultrasound field of high viscosity mixtures: Experimental and numerical investigation of a lab scale batch reactor

“…Various qualitative and quantitative methods are available in order to characterize the sonochemical activity inside a reactor. Possible effects related to the sonication of a medium include acoustic pressure and local temperature increase [12] , viscosity decrease and free radicals formation due to water dissociation [13] . Physical and physicochemical effects, such as the modification of solid surfaces, are also possible [13] , [14] .…”