The Flowability of Fine Powders in Reduced Gravity Conditions

摘要

The extrapolation of Qian's semi-theoretical relationship for the transition between cohesive andnon-cohesive powder fluidization behavior into regions of low gravity is studied and a validationexperiment employing fluidization is discussed. The fluidization experiment utilized fine glassand alumina powders in a fluidized bed and was flown onboard NASA's reduced gravity aircraft.The transition region between cohesive and non-cohesive behavior is determined for the glassand alumina powders at gravity levels of 1.8g, 1.0g, 0.38g, and 0.16g. The results are comparedto Qian's model and show fair agreement. The fluidization experiment limitations are discussedand a rotating drum experiment that will reduce the experiment uncertainty, provide quantifiableresults, and is suitable for flight onboard NASA's reduced gravity aircraft is proposed. Therotating drum technique determines the characteristic frequency of the powder's center of area todetect avalanching. The concept is validated by comparing the characteristic frequency obtainedfrom analyzing a cohesive powder to the characteristic frequency obtained from analyzing aflowable powder.