Study on aerosol agglomeration using the airborne ultrasonic transducer

Acoustic agglomeration technology use high-intensity acoustic field to make aerosol particles collide and condense rapidly. Existing studies have shown that 70%–90% of fine particles can be eliminated within minutes using compression drives and air-jet generators. Currently, there are limitations to the sound sources used. In this paper, an airborne ultrasonic transducer with a resonant frequency of 15 kHz is designed, followed by the corresponding numerical simulation and experiments for the evaluation of the vibration modal and sound pressure field. The sound pressure levels (SPL) of the open space and the agglomeration chamber can reach 150 dB and 156 dB, respectively. The agglomeration effect of water droplets, liquid phase smoke, solid phase smoke and mixed smoke is experimentally investigated, and the light transmittance rapidly increases from 8% to 60% within 4 s, 8 s, 5 s and 6 s, respectively. Agglomeration is also effective in the high-frequency range, and we infer that the acoustic wake effect is the predominant mechanism. The elimination effect is promoted with the increasing of SPL until the corresponding secondary acoustic effect is enhanced. Moreover, the agglomeration rate of higher concentration aerosol is significantly better than that of diluted aerosols in ultrasonic agglomeration process.