The use of shrouded supersonic jets for enhancing the performance of top blown metallurgical reactors has been studied using BOF pilot scale facilities set up in the MMPC's water modelling laboratory. The experimental results for three different designs of shrouded supersonic jet nozzles have demonstrated that greater depths of penetration and reduced mixing times can be achieved with co-axial sub and supersonic jets flow. Dimensional analysis indicates that the depth of penetration of a gas jet into a liquid bath depends on the height, H, of the lance tip from the quiescent bath, the liquid's Froude, Reynolds and Weber numbers, reflecting the ratios of gravity, viscous and surface tension forces to the jet's inertial, or momentum, forces. Good agreement between the mathematical model and experiments were obtained in terms of predicted and observed depths of penetration. Further efforts have been made to study jet penetration into liquid metals. The effects of density of liquid metal and a wide range of gas flow rates on the penetration depth were investigated theoretically. The results confirm that jet penetration depth can be increased with increasing shroud gas flow rate and decreased bath density.