Browse Prior Art Database

Particle Classifier

IP.com Disclosure Number: IPCOM000104085D
Original Publication Date: 1993-Mar-01
Included in the Prior Art Database: 2005-Mar-18
Document File: 2 page(s) / 57K

Publishing Venue

IBM

Related People

M Tzeng, H: AUTHOR

Abstract

Disclosed is a method and a disk-fuge apparatus for fractionating, at high flow rates, particles in the micron to supermicron range. It is based on differential centrifuging forces acting on particles of different sizes. A particle of diameter d sub p and density rho sub p rotating at omega in a flow experiences a centrifugal acceleration of magnitude where R is the radius. Assuming the particles obey the Stokes's drag law, it can be shown the terminal radial velocity, V sub r, is / <18 mu sub f> where mu sub f is the dynamic viscosity of the fluid surrounding the particle. It is noted that V sub r is proportional to d sup 2 sub p, i.e. larger particles drift radially outward faster than smaller ones.

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Particle Classifier

      Disclosed is a method and a disk-fuge apparatus for
fractionating, at high flow rates, particles in the micron to
supermicron range.  It is based on differential centrifuging forces
acting on particles of different sizes.  A particle of diameter d sub
p and density rho sub p rotating at omega in a flow experiences a
centrifugal acceleration of magnitude <omega sup 2 R > where R is the
radius.  Assuming the particles obey the Stokes's drag law, it can be
shown the terminal radial velocity, V sub r, is <R omega sup 2 d sup
2 sub p rho sub p> / <18 mu sub f> where mu sub f is the dynamic
viscosity of the fluid surrounding the particle.  It is noted that V
sub r is proportional to d sup 2 sub p, i.e. larger particles drift
radially outward faster than smaller ones.  When an axial flow is
imposed on the swirling flow, particles of different sizes are
segregated in the axial direction due to disparities in their radial
drift velocities.  The axial distance a particle travels, l, as it
moves from a radius of R sub i to R sub o is given by
l=<[18 <mu sub f> W]> over <[omega sup 2 <<d sub p> s2> <rho sub p>]>
'ln' <<R sub o> over <R sub i>>
where W is the imposed axial velocity.  For a fixed W, the above
equation yields l ' ' pro ' ' <1 / <<d sub p> sup 2>> .  Therefore,
the aerosol will be fractionated, or classified, in the flow
direction according to their size: larger ones deposit closer to the
flow entrance; smaller ones farther away from t...