The Fragmentation Analysis And Energy Transformation Ratio For Explosion Of Molten Aluminum In Water

As a light metal material, aluminum has an important significance in our modern life,but explosion accident induced by molten aluminum and water gradually becomes one of themost serious hazards in aluminum industrical production. Such accident accouts for thermalexplosion due to rapid vaporization of water in inclosed space by improper contact of moltenaluminum and water. Although numbers of research on this issue have been performed byoverseas researchers, no thorough and accurate mechanisms have been published, either nostudies on this problem have been carried out in domestic. Experiment, academic analysisand numerical simulation were used to study the reactions of molten aluminum and water. Amathematical model was established to describe the expansion work done by melt-watermixed system, the processes of heat transfer, deformation and fragmentation of moltenaluminum were also analyzed.Explosion accident induced by contact of molten aluminum and water belongs to thecategory of physical explosion. In the process of explosion, generous heat is continuouslytransformed into thermal energy, mechanical energy, light energy etc. The analysis ofinterface instability shows R-T instability, K-H instability and boundary layer shear effectcan cause unstable perturbation on fluid interfaces, which will bring to fluctuation ordeformation on the fluid interfaces, even can lead fragmentation. Energy used to form theshock wave just accounts for a small part of the whole explosion energy, most of the energyis transfered into kinetic energy or retains in the original aluminum. Energy transformationratio is recommend as a standard to estimate the intensity of explosion.Using the self-designed experimental conditions, the processes of intermixing andthermal explosion of molten aluminum and water were achieved by a pulling bottom plugmethod. The experimental results show that the energy transformation ratio of the explosionaccident induced by molten aluminum and water is very small, the maximum tested in theexperiment is7.95%, which illustrates the fact that only a small part of energy is transformedinto shock wave energy, majority of the energy is retained in the aluminum or somehowdissipated. The results also show that both the energy of explosive source and energy ratiowill increase along with the increase of aluminum temperature.Using the computational fluid dynamics(CFD) software, the models were build andapplied to numerically simulate the process of molten aluminum contacting with water. Firstly the free interface tracking technique coupling Volume of Fluid method was used tosimulate the dynamics process of film boiling on high temperature droplet. The evolution ofinstability at interface and growing bubble were captured clearly, and the distributions oftemperature and pressure are consistent with those from literature. Secondly free interfacetracking technique coupling Volume of Fluid method was used again to observe thedeformation and fragmentation of aluminum jet under the affect of hydraulic effect andthermal effect, the evolution of instability at interface and the process of aluminumdeformation and fragmentation were captured clearly, comparison of the deformation andfragmentation under the different affects was carried out to analyze the differences ofpressure field and velocity field under the two different situation.