Burning velocity of pyrotechnic compositions at various compaction pressures

Abstract. Pyrotechnic compositions are energetic materials consisting of intimate mixture between a reducer, generally a metallic fuel, and an oxidizer. The reactivity of these types of materials is affected by intrinsic characteristics and operating or experimental conditions. Hence, this study aims to investigate the influence of fuel particle size and compaction pressure on the burning velocity of iron-rich Fe/CuO pyrotechnic compositions. This will be achieved by defining three iron particle size classes (0–20 microns, 20–40 microns, and 40–80 microns) and by varying the compaction pressure between 115 and 260 MPa for two Fe/CuO compositions, namely 50 wt.% Fe / 50 wt.% CuO and 60 wt.% Fe / 40 wt.% CuO. Combustion experiments were achieved using a butane torch, and the tests were recorded using a high-speed camera operating at 420 fps. The burning velocity was then determined using a MATLAB-based image processing code that analyzes the flame front propagation from the recorded videos. The first analysis shows that increasing the compaction pressure improves mechanical cohesion of the samples and the pellet densities ranged between 4 and 5 g/cm³, corresponding to 50-70% TMD (Theoretical Maximum Density). These density variations provide insights into the dominant mode of mass and heat transfer within the pellets (conduction or convection). Moreover, we observe that the burning velocity is significantly affected by the compaction pressure of the Fe/CuO mixtures. Lower pellet densities (higher porosities) appear to enhance the burning velocity.