A Comprehensive Examination of Combustion of Magnesium-Water Mixtures

A comprehensive examination of the combustion of magnesium-water mixtures is conducted. A multizone flame model is developed to analyze the combustion of Mg-water mixtures. Mass, momentum, and energy equations are solved numerically in different zones by applying suitable boundary conditions at the interfacial boundaries. The study attempts to achieve a deeper understanding of the underlying processes, such as boiling of liquid water, heat transfer in multi-phase mixtures, chemical reactions, and multiphase flow dynamics. Further, the effect of thermophysical and transport property models on model predictions is examined. An attempt is made to decipher the microstructure of Mg-water mixtures and to identify a suitable effective thermal conductivity model. The dynamics of the boiling of liquid water is carefully studied by considering relevant physical processes such as bubble nucleation and growth, and by considering the possibility of superheating. A comparative analysis of different particle consumption models is also conducted. The effect of particle motion on combustion is studied using state-of-the-art drag models to account for physical processes prevalent in densely packed mixtures, such as the formation of particle clusters and flow constriction. The study highlights the importance of accurate property models, including the use of microstructure-compatible effective thermal conductivity model, and the significant effect of particle motion on the burning rates. The deficiencies and limitations of the 1-D Mg-water combustion models have been identified, and specific directions for future studies are provided.