The impact of multiple startups and startup parameters on the mass flow rate characteristics of powder fuel

To clarify the impact of multiple startups and startup parameters on the mass flow rate characteristics of powder fuel in a powder ramjet engine, this paper employs experimental and modeling methods to conduct an in-depth analysis of the fluidization and transportation characteristics of boron-based powder fuel under different startup conditions. The results demonstrate that the intake process of the first startup compresses the volume of the powder fuel, and during the working phase, the powder fuel's stacking profile evolves from a flat surface to a conical surface. These factors result in a longer mass flow rate response delay in the first startup (Δt = 9.4 s) compared to the second startup (Δt = 2.8 s). Presetting the stacking profile of the powder fuel as a cone and increasing the initial pressure of the storage tank to 0.17 MPa can significantly shorten the powder mass flow rate response time in the first startup, to Δt = 3 s and Δt = 0.54 s, respectively. The obstruction of the powder fuel at the intake position causes pressure fluctuations, with frequencies ranging between 2 and 4 Hz. The reaction force of the conical inner wall surface has a greater volume compression effect on the powder fuel than the intake process alone. Furthermore, the powder mass flow rate model based on the powder compression equation can accurately predict the powder mass flow rate during the stable supply phase, with a prediction accuracy of 3.1%.