Bubbling-jetting phenomena in powder injection into liquid.

Abstract

To know the effect of injecting powder with gas on the bubbling-jetting transition, an experimental study has been made on powder injection into a liquid. The gas powder mixture was injected into a water bath through a nozzle of 0.2cm in I.D. installed at the vessel bottom. The powders used were glass beads of 105-149μm, 177-210μm, and 350-420 μm. The mixture jet behavior was photographed by a high speed cinecamera. The injecting pressure was measured at the entrance to the nozzle.It is found that injecting powder with gas produces a drastic effect on the bubbling-jetting transition. The critical gas flow velocity for the initiation of jetting decreases in powder injection with increasing solid-to-gas mass ratio. This decrease in the critical gas flow velocity is found to become a larger extent for powders of smaller size. These findings could be ascribed to the fact that the velocity of sound of gas solid mixtures decreases with increasing the mass ratio and this decrease in the sonic velocity becomes a larger extent for powders of smaller size.