Aerosol impactors: calculation of optimum geometries

Optimum properties of particle inertial impactors for a two-dimensional ideal fluid are derived using conformal mapping techniques and improved numerical methods. Results of sequential calculations of one-dimensional contour integrals are matched with analytical expressions for fluid properties near the stagnation point. Particle trajectories are numerically simulated for a range of jet-to-plate spacings and fluid deflecting plate angles. These results are compared with the calculations of Davies and Aylward for a deflecting plate angle beta =90 degrees . It is found that an unconventional angle beta not=90 degrees exists for a given jet-to-plate spacing which maximises the slope of the particle efficiency curves. Although the conclusions are derived for an ideal fluid (Re= infinity ), similar results should apply for impactors operating at finite Reynolds numbers.