Optimization of a Cyclone to the 1993 International Sampling Convention for Respirable Dust

Abstract

A personal sampling cyclone, based on Higgins and Dewell's design, has been modified to obtain a virtually perfect fit to the international sampling convention for respirable dust. The cyclone penetration curve has been manipulated by varying vortex outlet pipe dimensions (vortex tube length and inner and outer vortex tube diameter) and the flow rate. A statistical experimental design was used to determine which combinations of vortex tube dimensions and flow rate should be tested. The vortex tubes were machined and the cyclone penetration curves were determined experimentally using a polydisperse polystyrene aerosol and a time-of-flight particle counter. The measured penetration curves' dependence on vortex tube dimensions and flow rate was fitted using multiple regression. It was found that the penetration was mainly dependent on vortex tube inner diameter and flow rate, and to a lesser degree on vortex tube length. As the vortex tube inner diameter was reduced, the penetration curvature became more pronounced. The relative deviation between modeled penetration and the sampling convention was determined. It was found that the optimal penetration curve was obtained for a flow rate of 1.9 L/min, a vortex tube length of 14 mm, and vortex tube inner and outer diameters of 2.1 and 4.0 mm, respectively. The bias in mass concentrations relative to a hypothetical sampler perfectly following the sampling convention for respirable dust was estimated to be less than ±8 percent.