Particle collection efficiency of an inertial impactor with porous metal substrates

This study has investigated numerically the particle collection efficiency of an impactor with porous metal substrates. Two-dimensional flow field in the inertial impactor was simulated by solving the Navier-Stokes equations with the control volume method. Particle trajectories were then calculated to obtain the collection efficiency at different Reynolds numbers, which are based on nozzle diameter, and at different K, which is the resistance factor of the porous metal substrate. This study shows that some air may penetrate into the porous metal substrate resulting in different particle collection efficiency than that predicted by the traditional theory. The particle collection efficiency for the impactor with the porous metal substrate is higher than that with the flat plate substrate below the cutpoint, and numerical results are in good agreement with the experimental data. The dimensionless parameter phi = (rhoU(0)/2K mut)(D-c/W)(0.9) has been introduced to determine the excess particle collection efficiency, eta (e), by the porous metal substrate in the limit of root St --> infinity. The theory explains the experimental data of the excess collection efficiency very well. (C) 2001 Elsevier Science Ltd. All rights reserved.