Equilibrium-Based Aluminum Drop Combustion Modeling

When including effects of aluminum particle combustion into larger simulations of explosives or propellant flows, a common approach is to rely on correlations at the particle-level for burn time and/or reaction rate. These correlations have been extensively documented in the literature and the relation between particle size and burn speed is well-understood (the “D-squared law”). However, much of the data supporting these correlations exist only for a limited range of pressure, temperature, and oxidizer compositions. Applying them to a complex combustion flow or extending them to other metals often involves significant extrapolation beyond the original data and is a source of uncertainty and potential simulation error. In this work we present an equilibrium-based superadiabatic flamelet model of a single drop combustion process that can be used to evaluate against common burn time correlations in spaces beyond where experimental data is readily available. This model is substantially (1000x) faster than a comparable model using finite-rate chemistry. We use it to examine the ignition/extinction space, examine the effect of crossflow velocity, and compare the model predictions with various burn time correlations across a range of aluminum droplets diameters.