Influence of particle size and shape on performance of reverse displacement piston powder feeding device

The powder fuel feeding system directly affects the operating stability, safety and thrust performance of the powder-fueled ramjets. Therefore, a reverse-displacement pneumatic piston powder feeding device was proposed. The effects of aluminum powder particle size and morphology on the steady-state feeding process were analyzed via a coupled Fluent-EDEM simulation.The results show that a stable packed layer is formed at the bottom of the powder hopper during feeding, with a conical particle pile accumulating beneath the feeding pipe. The airflow drives the aluminum powder to converge toward the center for continuous conveying, forming a dynamically stable powder particle distribution. Decreasing particle size markedly improves feeding efficiency. When the particle size is reduced from 150 μm to 50 μm, the efficiency rises by around 47.8%. Aluminum powders with aspect ratios ranging from 1∶1.5 to 1∶2.5 promote the rapid formation of a stable flow regime. However, the steady-state mass flow rate is decreased by about 15% when the aspect ratio reaches 1∶2.5. In summary, it is recommended that aluminum powder with a particle size of 50 μm to150 μm and an aspect ratio less than 1∶2 should be used in this feeding device.