The Virtual Cyclone: A Device for Nonimpact Particle Separation

Abstract

ABSTRACT. The virtual cyclone, a geometrically uncomplicated device that separates particles from a flow stream by nonimpact particle separation, is discussed. In contradistinction to a cyclone, the particle-laden flow is deflected from its original direction by a wall that curves away from the original flow direction, rather than into it. The computational fluid dynamics code FIDAP (Fluid Dynamics International) is used to perform two-dimensional fluid-flow and particle-motion calculations for a representative device geometry. Flow patterns are found to be insensitive to Reynolds number for values above 100 regardless of whether the flow is laminar or turbulent. Particle-motion calculations for laminar-flow cases indicate that the virtual cyclone geometry examined accomplishes nonimpact particle separation. An approximate analytical relation describing virtual cyclone nonimpact particle separation is developed and found to be in agreement with the numerical simulations. AEROSOL SCILNC'E AND TECHNOL~GY 26:X-573 (1997) O 1997 American Association for Aerosol Research NOMENCLATUREnormalized drag coefficient, 1 for R e , = 0 particle diameter unit normal vector gravitational acceleration (vector) inlet width width in third dimension, normal to plane of calculation particle radial position at inlet radius of curvature at inner edge of inlet radius of curvature at outer edge of inlet, R , = R , + H Reynolds number for fluid, Re = pU(2 H )/IL local Reynolds number for particle, Re,

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