Particle Focusing Characteristics of Sonic Jets

High-speed particle beams have found extensive applications in physical and chemical characterization of airborne particles. Expanding a particle-laden gas through an orifice into an evacuated chamber may generate these beams. Such particle inlets transmit a narrow particle size range, and this optimal size range strongly depends on the nozzle geometry and operating conditions. In this work, the choked flow through the primary focusing element is simulated using the CFD code FLUENT to seek an understanding of the mechanisms behind the formation of particle beams and the governing parameters. The focusing process is simulated to validate experimental results for existing inlet geometries and further used to evaluate novel inlet geometries that obtain higher transmission and focusing efficiencies. The best geometries yield particle transmission rates that are about 13 times higher than current designs.