The flowability of fine powders in reduced gravity conditions

Abstract

The extrapolation of Qian’s semi-theoretical relationship for the transition between cohesive and non-cohesive powder fluidization behavior into regions of low gravity is studied and a validation experiment employing fluidization is discussed. The fluidization experiment utilized fine glass and 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 glass and alumina powders at gravity levels of 1.8, 1.0, 0.38, and 0.16 g. The results are compared to Qian’s model and show fair agreement. The fluidization experiment limitations are discussed and a rotating drum experiment that will reduce the experiment uncertainty, provide quantifiable results, and is suitable for flight onboard NASA’s reduced gravity aircraft is proposed. The rotating drum technique determines the characteristic frequency of the powder’s center of area to detect avalanching. The concept is validated by comparing the characteristic frequency obtained from analyzing a cohesive powder to the characteristic frequency obtained from analyzing a flowable powder.