Ultrasonic agglomeration of flowing aerosol particles: Experiments and fixed pivot-based spatial population balance modeling

Abstract

Acoustic agglomeration (AA) is a promising technology for pre-conditioning of aerosol particles in industrial and civil settings. Although substantial experimental and modeling studies have been separately conducted under the temporal AA framework, systematic parallel experimental and numerical studies towards a deterministic spatial AA framework that may involve complex spatial inhomogeneity have few been executed yet. Here, we experimentally investigate the effects of ultrasonic agglomeration on spatial population evolutions of flowing aerosol particles. Parallelly, we develop a numerical algorithm that adapts the fixed pivot approach to perform the AA-induced spatial population balance modeling (FP-SPBM). Using this algorithm, the dependency of spatial AA performance on different parameters under both traveling-wave and standing-wave ultrasonic fields are numerically investigated. The results indicate that for a standardized initial particle size distribution (PSD), the peak position of particle number concentration (PNC) gradually shifts larger and the PNC peak drops continuously with spatial position under ultrasound. Specifically, across a 5-m distance, the position of PNC peak shifts from 2 μm to 2.4 μm, and the corresponding PNC peak drops by around 6.6 × 10⁴ #/cm³ with the sound pressure level, flow speed, and initial total PNC of 140 dB, 1 m/s and 1 × 10⁵ #/cm³, respectively. This study successfully captures spatial population evolutions of aerosol particles caused by AA, paving a way to the AA designs of spatial operation conditions. Moreover, the FP-SPBM methodology can perform SPBM under complex acoustic scenarios and can become an efficient design tool to maximum spatial AA efficiencies for practical applications.