Date of this Version
Aerosol Science and Technology, 44:253–261, 2010
A prototype multi-stage cyclone system consisting of an impaction inlet and five axial flow cyclone stages has been developed to classify simulants of Lunar and Martian dusts for various research and development needs of NASA’s space exploration missions. Individual axial flow cyclone stages can be either independently operated with an inline connection to other particle devices or cascaded together for particle separation and collection. The impaction inlet and first three cyclone stages were designed to operate at the flowrate of 50 lpm under pressure close to ambient. The last two cyclone stages were designed to operate under low pressure conditions to separate particles with diameters less than 200 nm. Due to the limited vacuum capacity of the pump used, the flowrates of last two cyclone stages were restricted to 11.0 and 1.0 lpm when operating the assembled prototype. The impaction inlet and each cyclone stage of the prototype were experimentally calibrated, and the cutoff particle sizes were 11.3 μm, 0.97 μm, 550 nm, 255 nm, 109 nm, and 40 nm.
It was further found that in general the flow Reynolds (Re) and particle Stokes numbers (StK) were critical parameters to characterize the performance of the axial flow cyclone stages, and the relationship between Re and the dimensionless cutoff size ( √ StK) was established. In addition, the collection efficiency curves are shifted to a smaller size range with a decrease of the cyclone pressure. However, using √ StK as the abscissa and keeping the same Re, the particle collection curves at different pressures can be merged into one. This study also found that the upstream pressure should be used to calculate StK instead of the average of upstream and downstream pressures of the test cyclone stage.