Development of a Cyclone-Based Aerosol Sampler with Recirculating Liquid Film: Theory and Experiment

• Published in: Aerosol science and technology 2006-05, Vol.40 (5), p.293-308
• Main Authors: Sigaev, Gennady I., Tolchinsky, Alexander D., Sigaev, Vladimir I., Soloviev, Konstantin G., Varfolomeev, Alexander N., Chen, Bean T.
• Format: Article
• Language: English
• Subjects: Aerosols; Liquids; Particle accelerators
• ISSN: 0278-6826; 1521-7388
• DOI: 10.1080/02786820600596891

This article describes the theoretical considerations, design criteria, and experimental performance of a cyclone-based, liquid-film, bioaerosol sampler. Different from conventional cyclones, this novel sampler draws air tangentially into the bottom of a swirling cyclone, creating a negative pressure differential which causes continuous suction of sorption liquid from its reservoir into the cyclone. The liquid swirls with the air vortex and rises spirally along the sampler wall in the form of a thin film. In the presence of an excess pressure differential, the liquid goes over the upper edge of the cyclone (overflow mode) and flows back to the bottom of the sampler. As a result, there is a continuous circulation of the sorption liquid in the sampler, which enhances the efficacy of capturing viable aerosol particles from incoming air. In this study, mathematical models using simplified Navier-Stokes equations are developed to describe the behavior of the airflow, the formation of the liquid film, and the precipitation process of the aerosol particles. Numerical solutions are presented as an approximation to these complex air and liquid flow streams in the whirlwind cyclone. Based on the theoretical assessment, practical design criteria for a novel sampler were formulated and a series of prototype samplers were fabricated and evaluated. In this report, experimental findings concerning the thickness of the air vortex, the pressure profile in the cyclone, and the apex height of the liquid film are presented. The results are in good agreement with theoretical prediction. However, the theory seems to overestimate the capturing efficiency for particles around the cutoff size (in the study, 1-2 μm) when comparing with data obtained from the experiments.