Coalescence characteristics of supersonic jets from multi-nozzle oxygen lance in steelmaking BOF

Hydrodynamic behaviors of multiple supersonic jets, especially their coalescence, are of paramount importance to effective design and operation of the oxygen lance in steelmaking basic oxygen furnace (BOF) but not well understood. This paper presents a numerical study on the coalescence of supersonic jets from the multi-nozzle oxygen lance at a practical Mach number by a compressible and non-isothermal computational fluid dynamics model. The model is firstly validated and then used to study the effects of key variables (i.e. ambient temperature and arrangement of nozzles including inclination angle and number) on coalescence behavior under various operational conditions. The results show that the jets prefer to deviate from their own nozzle axes and tend to coalescence with decreasing ambient temperature/nozzle inclination angle or increasing nozzle number. The attenuations of the velocity and dynamic pressure at the jet centerline are delayed with the increase of ambient temperature or the decrease of nozzle number/inclination angle. The critical condition where the jets are free from interaction is identified with increasing nozzle inclination angle, and the critical value is 25? for the four-nozzle lance considered. The simulation results are then used to estimate the cavity shape and splashing modes in BOFs.