Trapped vortex particle-to-vapor converter
First Claim
1. An apparatus for selectively separating a volatile constituent of particles from a flowing gas stream for analysis, which comprisesa housing with an inlet flow duct opening from an intake port that receives the gas stream at an upstream end at a first flow rate as driven by a pressure differential applied to said gas stream, said inlet flow duct with an enclosing wall therearound, and an outlet flow duct having an exhaust port at a downstream end for exhausting said gas stream therefrom;
- a trapped vortex cavity communicating with and adjoining said inlet flow duct, wherein said trapped vortex cavity is bounded by superior, lateral, inferior, and posterior, surfaces, and an anterior opening to said inlet flow duct, said inferior surface extending longer toward said inlet flow duct than said superior surface;
said inferior surface of said cavity defines an upstream-facing step with diverter lip that extends toward flow lines of said gas stream when said gas stream flows through said inlet flow duct, partially constricting the flowing gas stream, and defining an inertial particle impactor face, such that said particles in said flowing gas stream impact against said upstream-facing step, and wherein said superior surface of said cavity defines a downstream-facing step that terminates at a junction flush with said inlet flow duct;
said diverter lip extending beyond said downstream facing step toward said gas stream flow lines, whereby a trapped vortex of said gas is created in said vortex cavity when said gas is flowing through said inlet flow duct and said outlet flow duct;
a sampling outlet defined through an internal surface of said trapped vortex cavity, wherein said outlet is enabled for aspirating and collecting a gas sample volume from said cavity at a second flow rate, said second flow rate having fractional value of said first flow rate.
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Accused Products
Abstract
Apparatus and methods for selectively separating a volatile constituent of a particle from a gas stream for analysis. Particles are separated from bulk flow by inertia and impacted in a cavity containing a small but stable vortex or eddy. Heat is applied to volatilize constituents of the particles. The gas entrained within the vortex, which exchanges only slowly with the bulk flow, is withdrawn for analysis. In this way, a high volume flow containing particles of interest is reduced to a low volume flow containing a vapor concentrate. Advantageously, the apparatus may be operated at very low pressure drops in fully continuous, semi-continuous or batch mode according to the requirements of the downstream analytical unit. The apparatus finds use in active surveillance, such as in use of aerosols to detect explosives or chemical residues on persons, vehicles or luggage in real time.
28 Citations
20 Claims
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1. An apparatus for selectively separating a volatile constituent of particles from a flowing gas stream for analysis, which comprises
a housing with an inlet flow duct opening from an intake port that receives the gas stream at an upstream end at a first flow rate as driven by a pressure differential applied to said gas stream, said inlet flow duct with an enclosing wall therearound, and an outlet flow duct having an exhaust port at a downstream end for exhausting said gas stream therefrom; -
a trapped vortex cavity communicating with and adjoining said inlet flow duct, wherein said trapped vortex cavity is bounded by superior, lateral, inferior, and posterior, surfaces, and an anterior opening to said inlet flow duct, said inferior surface extending longer toward said inlet flow duct than said superior surface; said inferior surface of said cavity defines an upstream-facing step with diverter lip that extends toward flow lines of said gas stream when said gas stream flows through said inlet flow duct, partially constricting the flowing gas stream, and defining an inertial particle impactor face, such that said particles in said flowing gas stream impact against said upstream-facing step, and wherein said superior surface of said cavity defines a downstream-facing step that terminates at a junction flush with said inlet flow duct; said diverter lip extending beyond said downstream facing step toward said gas stream flow lines, whereby a trapped vortex of said gas is created in said vortex cavity when said gas is flowing through said inlet flow duct and said outlet flow duct; a sampling outlet defined through an internal surface of said trapped vortex cavity, wherein said outlet is enabled for aspirating and collecting a gas sample volume from said cavity at a second flow rate, said second flow rate having fractional value of said first flow rate. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20)
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Specification