2022 Volume 59 Issue 5 Pages 212-218
This paper describes separation performance of newly developed forward cyclones with 7 kinds of size and structure. The forward cyclones have 2 or 4 tangential-air-inlets, a dust pot and a flow receiver for fine particles. Our previous study showed that the cyclones had sharp size separation performance for PM2.5 but did not clarify the mechanism. Size separation characteristics of the cyclones were evaluated using a pair of optical particle counters with test aerosols of standard polystyrene latex particles ranging from 1 to 6 μm in diameter. Also swirling flow in the cyclone was observed by tracer powder. Measured data, such as 50% cut-off aerodynamic diameter at flow conditions of each cyclone, were used to estimate the flowrate branching off the dust pot. Ranging from 3 to 30 percent of total flowrate were passed to the dust pot before flow throughout the cyclone. The flow caused sharp centrifugal separation to the aerosol particles introduced into the cyclone. Smallest the cyclone (bore diameter was 10 mm) covered samplings for PM2.5 fraction of ambient aerosols at 3 L/min and respirable particle faction (PM4) at work environments at 1.7 L/min. Largest the cyclone (bore diameter was 90 mm) fitted to a high-volume air sampler of which flowrate ranged from 150 to 600 L/min, showed the same performance as the smallest one.
