Experimental study on eliminating fire smokes using acoustic agglomeration technology

Abstract

Acoustic agglomeration is a process in which an intense sound field is applied to promote relative motion and rapid agglomeration among aerosol particles. This technology is able to improve significantly and rapidly the visibility of the smoke in a fire situation, and therefore assists the quick evacuation of evacuees. In this paper, the elimination effect of polystyrene smoke using acoustic agglomeration technology is experimentally investigated. The results show that the smoke transmittance will be increased to 0.75 from the initial value of 0.24 in only 0.5 min, in a 1.5 kHz acoustic field at a sound pressure level of 141 dB. The agglomeration rate is sensitive to acoustic frequency and there is an optimal operation frequency, which indicates that the predominant mechanism is orthokinetic interaction. Under the conditions of our experiments, the optimal frequency for eliminating soot particles is determined to be 1.5 kHz. As an energy consuming process, the agglomeration efficiency increases proportionally with the acoustic power until the corresponding nonlinear acoustic effects become significant. Moreover, it is found that the agglomeration rate of thicker smoke is much higher than thin ones at the early stage of the process, but the discrepancy tends to vanish at the later stage.