Ignition and Combustion Process of Aluminum-Air Mixture by the Action of Thermal Jet

Powder-shaped metal fuel is applicated in some indurstial fields, and is of great potentiality in aerospace propulsion technology, especially Rotating Detonation Engine (RDE), but ignition and combustion characteritics of metal powder is in need of further research. This study investigates the ignition and combustion characteristics of aluminum powder/air mixtures under thermal jet action. An experimental system was designed, incorporating a thermal jet tube for ignition, a powder disperser, and a high-speed schlieren imaging system for visualization. Experiments examined the effects of aluminum powder particle size (100 nm, 1–2 μm, 20 μm) and thermal jet energy (varied via theoretical jet speed from 1082 to 1857 m/s). Results show that particle size significantly influences ignition behavior: 1–2 μm aluminum powder demonstrated optimal characteristics including successful ignition and sustained combustion, 100 nm particles exhibited good flow-following and short ignition delay (~9 μs), while 20 μm particles failed to ignite under the tested conditions. Furthermore, a critical thermal jet theoretical speed of approximately 1500 m/s was identified for reliable igniting the 1–2 μm powder/air mixture. These findings provide valuable insights into the ignition dynamics of metal powders in detonative condition and offer fundamental guidelines for designing and optimizing ignition systems in aluminum powder-fueled RDEs.