THEORETICAL CALCULATIONS OF THE COLLECTION EFFICIENCY OF SPHERICAL-PARTICLES AND FIBERS IN AN IMPACTOR

Collection efficiencies of two types of impactor nozzles were calculat ed for spherical particles and fibers. The flow field through the impa ctor was calculated for Reynolds numbers of 100 and 1100 using a finit e element method. Equations of motion for spherical particles and fibe rs were obtained and were used along with flow held information to cal culate impactor collection efficiencies. The calculated collection eff iciency for spherical particles agreed with that in the literature. Th e cutoff size at 50% agreed with experimental data, but the collection efficiency curve lacked a long tail at low collection efficiencies. F or fibers, collection efficiency curves were obtained in terms of fibe r Stokes number and aspect ratio. The calculated collection efficiency curve moved to higher Stokes numbers with increasing fiber aspect rat io. The cutoff size for fiber minor diameter decreased as the fiber as pect ratio increased. Copyright (C) 1997 Elsevier Science Ltd