A combustion front quenching technique is used to investigate the separation of reaction products during a fast self-propagating high-temperature synthesis (SHS) thermite reaction, which is applied to the aluminothermic welding of rails. Quenching of the reaction zone with a melt temperature at approximately 2400 K enables the possibility of analyzing intermediate stages during exothermic SHS type reactions and the prediction of a time duration for a complete separation of the products Fe, Al2O3, and intermetallics. An average separation time is then used to validate a 3D phase field solver phaseFieldFoam and solution parameters through application of the diffusive Cahn–Hilliard equation, also known as model B.

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The aluminothermic reaction is a type of self-propagating high-temperature synthesis to produce high quality metals and metal oxides en route. The main use of the aluminothermic reaction is in the field of railway welding. The multiphase flow of steel, slag and air in differently shaped crucibles has been numerically investigated in this work with the volume-of-fluid method. The simulations were carried out with the multiphase solver of the open source toolbox OpenFOAM. To validate the numerical results of the three-dimensional simulations, an experiment was carried out to investigate the discharge of a water-oil system from the crucible. A comparison to a numerical 3D simulation showed reasonable accurate results. It can be said that the solver is capable of predicting the point of the oil penetration of the water phase in the experiment.

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