Characterization of gas jet behavior at a submerged orifice in liquid metal.

Abstract

The present paper is concerned with a study made with the purpose of clarifying the behavior of injected gas jets especially at the exit of a submerged orifice in liquid metal. Nitrogen was injected into a mercury bath through an orifice of 0.1-0.4cm in diameter located at the transparent vessel bottom. The gas-flow rates were varied from 0.05 to 4500cm3/s at orifice conditions. The highest gauge pressure supplied to the system was 20kgf/cm2. Behavior of gas jets was observed directly through the bottom plate by using a high speed cinecamera. At low gas-flow rates the jet is shown to expand immediately upon discharging and form seemingly discrete bubbles. This behavior is called “bubbling”. With increased gas-flow rates, an apparent coincidence between the base diameter and the orifice diameter begins to occur over various time ranges. In these time ranges the injected gas is considered to leave the orifice as a continuous jet of gas. This phenomenon is called “jetting” and is found to occur in the sonic flow region. The change from bubbling to jetting takes place in a transitional gas-flow range. With increasing gas-flow rate jetting fraction increases and bubbling fraction decreases.