Influence of Acoustic Frequency and Particle Residence Time on Fine and Ultrafine Particle Agglomeration for Air Quality Control Applications

With increasingly strict air quality standards and growing concerns about air pollution, fine and ultrafine particulate matter remains a major challenge for conventional air cleaning technologies. Due to their small size, these particles are difficult to remove using traditional filtration and separation methods. Acoustic agglomeration can be used as a pre-treatment technology to increase particle size in a high-intensity acoustic field and improve the efficiency of particle removal. This study investigates acoustic-induced agglomeration of solid aerosol particles in a dynamic airflow system. The effects of acoustic frequency were evaluated at 3, 5.5, 7.5, and 15 kHz under a sound pressure level of 135 dB and at two airflow velocities: 0.75 m/s and 1.5 m/s. These velocities corresponded to different particle residence times in the acoustic field. Arizona test dust was used as the test aerosol, and particle-number concentration and particle-size distribution were measured before and after the acoustic field. The results showed that acoustic agglomeration of fine and ultrafine particles was strongly affected by both acoustic frequency and particle residence time. The highest agglomeration efficiency, reaching up to 42%, was obtained at 3 kHz, 135 dB, and longer particle residence time. These findings indicate that acoustic agglomeration can promote particle-size redistribution in moving airflow and may be used as a pre-treatment method for improving particulate matter removal in air quality control systems.