A MODEL FOR THE PREDICTION OF THE COLLECTION EFFICIENCY CHARACTERISTICS OF A SMALL, CYLINDRICAL AEROSOL SAMPLING CYCLONE

Velocity data from a previous study were nondimensionalized and used in conjunction with a computer program which solves the equations for particle trajectory to predict the collection efficiency for the cyclone. Results for the prediction of cutpoint at the same Reynolds number as that for which the velocities were measured, both for a large cyclone of 88.9 mm diameter and another geometrically similar at one half the scale, are excellent. The model predicts cutpoints of 10 μm and 5.1 μm for the large and small cyclone, respectively, while the actual cutpoints determined from aerosol tests were 9.9 μm and 5.2 μ m. The efficiency curve generated by the model was steeper (geometric standard deviation of 1.1) than the efficiency curve determined through the aerosol testing (geometric standard deviation of 1.4). A simplification of the Dirgo and Leith equation fitting Barth’s design curve is suggested which provides a significantly better fit of the aerosol data (geometric standard deviation of 1.3). At 1.5NRQ, where NRQ= (4pg)/(πμDc), the error in prediction of the cutpoint in the large cyclone is less than 8% while at 04NRQthe error is less than 2%. Although results are good over a limited range of Reynolds numbers, the model is strictly applicable only for flows which are dynamically similar to those studied here. © 1990 Elseiver Science Publishing Co., Inc.