Study of submerged air jets in liquids

Abstract

Submerged gas injection has attracted much attention due to its wide range of application in different processes. A number of numerical analysis has been made to investigate the stability of submerged air jet in liquids. Experimental studies are however scarce. In present study for the first time a systematic experimental study of submerged gas jet is made. Experimental investigation on submerged air jet was carried out in a 14x 14 cm2 Perspex column with a liquid height of 25 em. The jets were generated by flowing air at different velocities through nozzles immersed at the bottom of a stagnant liquid column. The diameters of the nozzles used were I, 4 and 6 mm. The jet formation was observed in three different liquids, namely, water, ethanol and glycerol. The minimum jet formation velocity was recorded and jet lengths at different velocities were measured by image processing. The data showed that the jet length increases as the velocity increases until it reaches a maximum value. Beyond this value, the jet length decreases as the velocity increases. The jet formation velocities as well as the jet lengths for all three gas/liquid systems are increased with decreasing nozzle diameter. Viscosity of the liquid was found to have a destabilizing effect on jet break-up length. The observed phenomena are explained with the aid of instability theory and compared with existing theoretical analysis.