The use of nonlinear acoustics as an energy-efficient technique for aerosol removal

This article is a feasibility study on using nonlinear acoustic effects, acoustic streaming and acoustic radiation pressure, for aerosol removal in an air duct. Unlike previous research, which used acoustics solely to cause aerosol agglomeration prior to aerosol removal in traditional duct collection systems, this article considers the acoustic streaming effect, which is significant but was previously neglected. Monodispersed polystyrene spheres with diameters ranging from 0.3 to 6 μm were tested. The proposed system removed 12-20% of the submicron aerosols and 25-32% of the micron aerosols when the airflow rate was approximately 90 L/min. Acoustic streaming introduces stagnation points on the surface of the air duct and removes the aerosols by deposition. Acoustic radiation pressure causes aerosols to form agglomerates. This enhances inertial impaction and/or gravitational sedimentation, which further enhances the removal efficiency of micron aerosols. The particle-removal efficiency is proportional to the duration that the aerosols are exposed to the acoustic field. The pressure drop due to the nonlinear acoustic effects is negligible; thus, power consumption is minimal. This system has the potential to be developed into an energy-efficient technique for aerosol removal.