Influence of Aerosol Inflow Direction on Virtual Impactor Performance

Abstract

For this research, a horizontal inlet was applied to the existing vertical virtual impactor, and then aerosol and clean air were added to the upper part of the inlet and the lower part of it, respectively. Then, the flow ratio of the aerosol and clean air was varied, to confirm changes in collection efficiency and wall loss according to the flow ratio. The separation performance of the virtual impactor could be improved by concentrating particles at the center when the existing vertical inlet was replaced with the horizontal one, but it could not resolve the problem caused by over-focusing. However, the problem of over-focusing caused when applying a horizontal inlet could be mitigated by adding clean air. As for PM2.5, PM5, and PM10 of the existing virtual impactor with a vertical inlet, the cut-off size when the shape of the inlet was changed was 2.1, 4.5, and 8.9μm, respectively. When compared to existing virtual impactors, the figure was a 16%, 10%, and 12.36% decrease, respectively. In addition, decrease of loss from the wall effect near the cut-off size from 18% to 1.2% was confirmed.