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. and 2cm in O. D. installed at the vessel bottom. The powders used were glass beads of 105149μ, 177210μ, and 350420μ. The mixture jet behavior was photographed by a high speed cinecamera. The injecting pressure at the entrance to the nozzle was measured.
It was found that injecting powder with gas produced a drastic effect on the bubbling-jetting transition. The critical gas flow velocity for the initiation of jetting, which in the case of gas injection was just equal to the sonic velocity, decreased in gas-powder injection with increasing powder to gas mass ratio. This decrease in the critical gas flow velocity was found to become more extensive 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 more extensive for powders of smaller size.