Characterization of fluidization instability in the initial development stage of dense powder pneumatic conveying.

This article focuses on the startup characteristics of powder fuel conveyance in powder-fueled ramjet engines, analyzed through coupled computational fluid dynamics–discrete element method (CFD–DEM) simulations. It examines how different fluidization gas inlet configurations, wall friction coefficients, fluidization pressures, and pre-pressurization levels affect the transient two-phase flow dynamics during the initial conveying stage. The study finds that center-internal gas injection offers superior conveying stability and performance compared to tangential-external and reverse-external inlets, while sufficient fluidization gas flow is essential to avoid unstable slug flow. Additionally, higher fluidization pressure accelerates stabilization but increases startup fluctuations, and increased wall friction reduces peak flow rates but delays piston stabilization; pre-pressurization helps reduce piston delay and prevents sudden drops in powder mass flow rate. These insights provide a foundation for optimizing powder supply system designs and operational parameters in powder-fueled propulsion technologies.