Numerical study on the characteristics of a nano-aluminum dust-air jet flame

Nano-sized aluminum dust is quite attractive in the application scenarios with limited residence time. This study simulated an aluminum nanoparticle-air jet flame in a burner that was proposed to characterize the mixing and burning properties of dust and air in a classical ramjet configuration. The model considers the flow of gas phase by employing three-dimensional multicomponent Navier-Stokes equations, and the aluminum particles via the Lagrange approach. A combustion sub-model was developed to characterize the heat convection, radiation and combustion processes of nano-sized aluminum particles. Thereafter, the model was validated by comparing with experimental results of dust jet flow and aluminum particle combustion. With the present model, the characteristics of flow field, and variations of particle temperature, heat release and statuses etc. were examined in detail, by which the mixing zone and flame structure were defined. The results showed that the nano-aluminum particles in the inner mixing layer were firstly ignited by the hot co-flow air and burned, and these particles in the core jet region were ignited downstream. Once the aluminum particles were ignited, they burned out promptly in this burner. The effects of particle size were evaluated, and the results show that the lengths of mixing layer and reaction zone, as well as the width of reaction zone reduce with decreasing particle size, whereas the width of mixing layer stays the same.