Digital Image Analysis of Two-Dimensional Fluidized Beds at Lunar Gravity

Fluidized beds are key hardware items for lunar oxygen production processes using hydrogen as a reducing agent. A Plexiglas two-dimensional bed was constructed to measure bubble sizes at lunar gravity on NASA's KC-135 aircraft to develop fluidized bed reactor design criteria. Four lunar simulants were filmed while fluidized at lunar gravity for digital analysis of the video data. Analysis revealed that a linear relationship clearly exists between bubble size and vertical bed position. A key observation was the size of the bubbles is inversely proportional to the particle density of the test solids. Solids with low particle density such as glass beads form larger bubbles than the more dense MLS-1 and Florida ilmenite fractions. Also, a theoretical correlation relating bubble rise velocity as a function of bubble diameter and gravity was verified by these tests. A comprehensive data set now exists making it possible to predict the bubble size and rise velocity of numerous lunar starting materials for fluidized bed lunar oxygen processes.