Design methodology for multiple inlet cyclones

Correlations were developed to model the performance of two types of multi-inlet aerosol sampling cyclones. The body of one cyclone had the Lapple conventional geometry and the other had a shorter design, which was one-half the length of the Lapple geometry. Four cyclones of each type were constructed, with body diameters of 38.1, 57.2, 88.9, and 139.7 mm. Each cyclone was tested at several flow rates, with the range of flow rates for the entire data set being from 9.4 L/min to 1027 L/min. Aerodynamic particle cutpoint diameters, D-0.5, were determined for several sets of test conditions, consisting of a given cyclone type and a fixed flow rate. The range of cutpoints determined in the experiments was 3.9-17.1 mu m aerodynamic diameter. Experimental data were correlated to a logarithmic-linear relationship: (C0.5D0.5)-D-1/2/d(c) = In a + b In Re-f where C-0.5 is Cunningham's slip correction for the cutpoint size; d(c) is the cyclone diameter; and, Re-f is the flow Reynolds number, which is characterized by the air inlet velocity and the width of the channel between the cyclone body and the outlet tube, The correlation coefficients, r(2), for data of the long and short multi-inlet cyclones to the log-linear model were 0.984 and 0.991, respectively. The log-linear relationship between the size parameter and the flow Reynolds numbers was re-arranged to provide working relationships for designers. Fractional efficiencies were measured for each cyclone, and sigmoid curves were fitted to the data that provide a relationship between fractional efficiency and dimensionless particle size, (D-a - D-0.5)/D-0.5, where D-a is the aerodynamic particle diameter.