Numerical study on the effect of nozzle-plate distance on the aerosols collection efficiency and deposition on the impaction plate of a multi-nozzle inertial impactor

Identifying the location of deposited particles on the impaction plate can help analyse them for mineralogical and geochemical purposes. So far, no direct studies have evaluated the effect of nozzle-plate distance (S) on the particle’s depositional arrangement in a multi-nozzle inertial impactor. In this study, an 8-nozzle inertial impactor with two different nozzle-plate distances, S 8.5 and S 10.5 mm, is simulated numerically using the Eulerian–Lagrangian approach. The effect of the parameter (S), particles’ aerodynamic diameters and shape factors on the collection efficiency, and particle distribution on the impaction plate are investigated. Particles with five various shape factors (∅ 0.4, 0.5, 0.7, 0.9 and 1) and six different aerodynamic diameters (da 1, 2, 2.5, 3, 5 and 6μm) are examined. Increasing the “S" has the most effect on particles with da 2.5μm, which reduces the collection efficiency by 11%, and particles’ efficiency reduction for the smallest and largest aerodynamic diameter studied in this paper (da 1μm and da 6μm) is negligible (less than 1%). Also, increasing the nozzle-plate distance increases the secondary depositions of particles on the impaction plate, which affect the smaller particles more; particles with da 1μm up to 23%, and particles with da 6μm less than 1%. Moreover, results showed that coarser particles deposit more and merely in front of the nozzle outlet on the impaction plate. Furthermore, spherical particles sediment more than non-spherical particles. Since analysing the selective particles take less time and cost, this research has proposed depositional arrangement of various particles on the impaction plate.