EXPERIMENTAL INVESTIGATION OF THE INSTABILITIES IN A FLUIDIZED-BED ORIGIN OF THE PRESSURE-FLUCTUATIONS

This Paper presents an experimental investigation of the hydrodynamic instabilities inside a self-excited fluidized bed. Pressure fluctuatio n and bed height measurements have been reported. In the slugging regi me (above a critical gas flow rate), the bulk is found to exhibit a re gular and periodic macroscopic pattern (large numbers of particles mov ing collectively in a seemingly organized manner). This state is chara cterized by nearly signoidal pressure fluctuations and regular bed hei ght oscillations. As the gas flow increases the bulk motion tends towa rd large oscillations with intermittent smaller ones. The pressure flu ctuations above the bed surface and the bed height oscillations are fo und to be intimately correlated. We report experimental evidence that the pressure fluctuations observed in a fluidized bed under and above its surface are caused by the oscillations of the bed height. The pres sure wave initiates at the surface of the bed and propagates both upwa rd and downward. (C) 1997 American Institute of Physics.