Classification Performance of Virtual Impactor

Abstract

Theoretical studies of separation efficiency of a virtual impactor have been conducted. It is found that the inertia parameter of 50 % partial separation efficiency becomes smaller as the ratio of slit width to pipe radius decreases, while it becomes larger as the ratio of straight to total flow rate or the flow Reynolds number in an inlet pipe decreases. Thickness of the pipe wall at the slit does not affect separation efficiency. Experiments are carried out by using 3 to 4 μm monodisperse methylene blue-uranine aerosol generated by a spinning disk. These experimental results agree well with the calculated values obtained by use of a potential flow model. The classification performance is slightly inferior to that of a conventional impactor. It is also observed that the amount of particles deposited at the inlet tip of straight-through pipe is not negligible under some operating conditions.