Investigation of collection efficiency of round-nozzle impactors at different atmospheric pressures and temperatures

Abstract

A simulation approach for predicting the collection efficiency of inertial impactors was developed by calculating particle trajectories in a Lagrangian reference frame. When numerically predicted collection efficiencies of the electrical low-pressure impactor (ELPI) were compared with the experimental data found in the literature, the agreement was good and the relative difference in cut-off size was less than 12%. Then, balloon-borne impactors having nominal cut-off sizes of 1 mu m, 2.5 mu m, and 10 mu m were designed, and their collection efficiencies were predicted using the present simulation approach. When volumetric sampling flow rate of air introduced to the single-stage round-nozzle impactors was fixed at varying altitude, the cut-off sizes were predicted to decrease from 0.98 mu m, 2.47 mu m, and 9.86 mu m at sea level to 0.47 mu m (by 52.0%), 1.70 mu m (by 31.2%), and 7.62 mu m (by 22.7%) at 16-km-altitude, respectively. When volumetric sampling flow rate was adjusted, the cut-off sizes of the single-stage round-nozzle impactors were estimated to remain almost unchanged with the variation of less than 5.1%, 7.3%, and 10.6%, respectively, at varying altitude in troposphere. (C) 2015 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.