Characteristics of Flow Field for Supersonic Oxygen Multijets with Various Laval Nozzle Structures

The Laval nozzle is used widely in steelmaking processes to increase the velocity of an oxygen jet up to approximately 2 Mach numbers. The present research is aimed at determining the effect of the Laval nozzle structure on a supersonic oxygen jet flow field. Both one-dimensional isoentropic flow theory and a characteristic-line method were used to design five-hole oxygen lances of two types and, applicable to oxygen multijets, to analyze their flow field characteristics by a series of numerical simulations and experimental studies. When compared to the conventional oxygen lance designed according to the one-dimensional isoentropic flow theory, the new oxygen lance designed with employment of the characteristic-line method is more effective in both suppressing the shock wave generation and improving the initial axial velocity of oxygen jets under the same test conditions. As a result, a larger impaction cavity was generated by the new oxygen lance and the mass transfer within oxygen, liquid slag, and molten steel was enhanced.