Collection Efficiency of Rectangular Slit-Nozzle Inertial Impactors with Impaction Plates of Elliptical Concave Curvature

Abstract

In this study, the impaction plate with an elliptical concave groove was employed in an effort to enhance the collection efficiency of the slit-nozzle inertial impactor. The major axis length (A) and the minor axis length (B) of the elliptical concave curvature were varied. The effect of the ratio of A to B on the collection efficiency of slit-nozzle inertial impactors was investigated both numerically and experimentally. The numerical results were in good agreement with the experimental data for different values of A/B ratio. The elliptical concave impaction plates were useful in not only reducing the particle bounce but also lowering the cut-off size. The optimum range of the A/B ratio was found to exist for minimizing the cut-off size. When the elliptical concave impaction plates with the A/B ratio of 2 were used for the slit-nozzle inertial impactors, the square-root of the Stokes number was estimated to be lowered from 0.77 to approximately 0.6, resulting in the decrease of the cut-off size by 22% compared with the typical flat impaction plates.