Electrodynamic Concentration of Non-ferrous Metallic Particles in the Moving Gas-powder Stream: Mathematical Modeling and Analysis

This paper presents theory, modeling, and analysis of a novel electrodynamic concentration approach for submillimeter-sized conductive metal particles focusing in moving gas-powder stream. Such method is of particular interest in blown-powder feeding fabrication industry (e.g., powder-fed additive manufacturing) to generate a tightly focused powder stream. Conceptual design of a concentration generator is proposed with two different configurations: The doublet Halbach permanent magnet quadrupoles (doublet-Halbach-PMQs) and the doublet electromagnet quadrupoles (doublet-EMQs). Analytical models for magnetic forces and concentration angles were built. Numerical calculations were conducted for pure aluminum particles with a radius of 50<Rp≤500 μm. It was found that the magnetic force and the concentration angle increase with an increase of the particle size. The numerical results indicate that the proposed concentration generator with doublet-Halbach-PMQs configuration cannot be effectively used for small-size particle concentration. By contrast, the concentration generator with doublet-EMQs configuration under high frequency is capable to concentrate particles with a radius of Rp>150 μm. The particles with a radius of Rp = 300 μm can be concentrated with more than 15∘ angle at the frequency of 600 kHz. Therefore, the proposed doublet-EMQs configuration has a great potential to generate a narrowed and finely focused powder stream in the blown-powder feeding fabrication process.