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

The startup characteristics of powder fuel conveyance significantly impact the reliable ignition of powder-fueled ramjet engines. By utilizing coupled computational fluid dynamics–discrete element method, this study took into full consideration the piston follow-up behavior, the interactions between solid particles and gas flow, as well as wall surfaces, and provided a more accurate analysis of the unsteady features during the initial development stage of dense powder conveying. The results show that the center-internal inlet exhibits superior powder conveying performance compared to that of the tangential-external and reverse-external inlets. While increasing fluidization pressure reduces conveying efficiency, it accelerates the stabilization process. Reducing the wall friction coefficient enhances the startup fluctuation, and pre-filling the powder chamber with gas decreases the piston delay and prevents the sudden drop in powder mass flow rate. This study advances the understanding of the two-phase flow mechanisms in the powder supply system and provides a valuable foundation for optimizing structural designs and operational parameters.