Development of a high-volume ambient aerosol sampling inlet with an adjustable cutoff size and its performance evaluation using road dust

Abstract

Aerosol samplers are generally classified into particulate matter (PM_2.5 or PM₁₀) and total suspended particle (TSP) samplers. As changing the cutoff size is cumbersome, it necessitates either replacing the particle size separator or adjusting the sampling flow rate. In this study, a novel high-volume aerosol-sampling inlet with an adjustable cutoff size was developed. Its performance was evaluated at a sampling flow rate of 1000 L/min of road dust. The cyclone separator installed with the newly developed inlet absorbed airflow from all directions. The cutoff size of this inlet was easily adjustable using the guide vane angle. For the guide vane angles of 29°, 42°, and 90° (at a 2 km/h freestream velocity), the cutoff sizes were 2.59, 9.92, and 26.2 μm, respectively. At the 90° angle of the guide vanes and the free stream velocity of 2 km/h, no rotational airflow occurred inside the cyclone separator to allow TSP sampling. Increasing the freestream velocity to 16 km/h at angles of 29° and 42° decreased the cutoff size by 0.12 and 0.45 μm, respectively; finely adjusting these angles further reduced the cutoff size to 0.04 and 0.07 μm, respectively. Thus, an almost constant cutoff size was possible. The developed inlet allowed sampling of PM_2.5, PM₁₀, or TSP using a single device.

Keywords: Adjustable cutoff size; Aerosol-sampling inlet; Omnidirectional inlet; PM(10); PM(2.5); TSP.