Mixing and solidification of a turbulent liquid jet in a co‐flowing stream

Abstract

SUMMARYA mathematical model has been developed to quantify the effects of process conditions during turbulent solidification and mixing of a liquid metal jet in a confined co-flowing molten metal stream.The modelling has been split into three parts. First, a single phase model with no latent heat effects to consider the solidification potential. Secondly, a two phase model where the second phase is comprised of solid particles which solidify during mixing of the two streams. Thirdly, a two phase model where the second phase consists of the inner jet, which is assumed to break up into droplets of given size, and solid particles are allowed to form by solidification within the droplets.The results show that the thermal history (solidification path) of the solid phase formed is affected by latent heat and particle sLe, which implies that solidification, nucleation and jet fragmentation events should be included dynamically to ensure realistic predictions. METALLURGICAL BACKGROUNDThe mechanical properties of metal alloys are controlled by their microstructure, which in turn is largely controlled by the solidification mode during casting. For a number of applications it is desirable to make the structure as fine and uniform as possiblc, and this can be achieved by solidifying the melt very rapidly.There are a variety of methods commonly used for achieving rapid solidification which involve fragmentation of a melt into droplets (e.g. atomization) or stabilkation of thin melt sections to produce ribbons or flakes (e.g. melt spinning),' but for most applications the resultant materials must be reconsolidated into a bulk product via elaborate and often costly fabrication routes. Moreover, the extensive thermomcchanical treatments involved in reconsolidating often result in a loss of mechanical properties in the finished product, due to the accelerated kinetics of solid state transformations. The 1 urbulent solidification process described here has bcen developed by Alcan International to help overcome the abovc kinetic constraints as well as avoiding the need to reconsolidate.The process is best described by reference to Figure 1. The final alloy composition is initially split inlo two components; a minor component ofhigh concentration and high melling point (feedstock)

A tribute to D.B. Spalding and his contributions in science and engineering

“…The successful use of PHOENICS-ESTER by the aluminium industry has already been mentioned. In addition Alcan International collaborated with CHAM to use IPSA in PHOENICS for simulating the mixing and solidification of submerged liquid metal jets, see Enright et al [218]. CHAM also used IPSA to create PHOENICS-based CFD models for the NASA Lewis Research Centre to simulate solidliquid phase change in binary materials, see Prakash [219,220].I n the mid-1980s CHAM also began work on developing a PHOE-NICS-based CFD model of the HIsmelt process, which involves the direct smelting of iron ore by injecting the iron and coal fines directly into a molten bath, plus the subsequent release and burning of the smelting gas in the top space.…”