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A system and method for particle separation in a gas turbine engine centrifugal impeller bleed air system using a tangential velocity component of the compressor bleed air to centrifuge the particles radially outwardly and convey the particles circumferentially, away from a clean air outlet and towa

A system and method for particle separation in a gas turbine engine centrifugal impeller bleed air system using a tangential velocity component of the compressor bleed air to centrifuge the particles radially outwardly and convey the particles circumferentially, away from a clean air outlet and towards a particle outlet where the particles are extracted from the bleed air.

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1. A particle separator for a gas turbine engine having a central longitudinal axis, comprising a generally toroidal cavity defined within a casing surrounding a compressor impeller gas path and being in gas flow communication therewith through a plurality of circumferentially interspaced bleed aper

1. A particle separator for a gas turbine engine having a central longitudinal axis, comprising a generally toroidal cavity defined within a casing surrounding a compressor impeller gas path and being in gas flow communication therewith through a plurality of circumferentially interspaced bleed apertures formed in said casing, the cavity being funnel-shaped such as to define a radially outer narrow tip circumferentially extending about the cavity, at least one clean air outlet being disposed in communication with the cavity and located radially inwardly from the radially outer narrow tip thereof, and a particle outlet radially located in a circumferential lower portion of the radially outer narrow tip of the cavity, the circumferential lower portion being disposed below the central longitudinal axis of the gas turbine engine in a normal flying attitude, the bleed apertures allowing bleed air from the compressor impeller gas path to flow into the cavity, during operation of the gas turbine engine, with a tangential velocity component sufficient to at least partially centrifuge particles present within the bleed air into the radially outer narrow tip of said cavity and convey the particles circumferentially thereabout to the particle outlet, wherein air flowing out from the clean air outlet is thereby substantially free of particles. 2. The particle separator of claim 1 wherein the bleed apertures are tangentially oriented within the casing. 3. The particle separator of claim 1 further comprising an annular baffle extending radially outwardly into the cavity, the annular baffle being longitudinally adjacent the bleed apertures and disposed between the bleed apertures the clean air outlet. 4. The particle separator of claim 1 wherein a tangentially facing scoop is disposed within the cavity proximate the particle outlet and oriented to receive incoming particles such as to guide incoming particles through the particle outlet. 5. A gas turbine engine having a compressor rotor rotatable about a main longitudinal axis of the engine and housed in a compressor case, the compressor case at least partially defined therewithin a toroidal internal cavity surrounding a gas path of the compressor, the compressor case having a plurality of circumferentially interspaced bleed apertures therein which provide gas flow communication between the gas path and the cavity, the compressor case having an air outlet in gas flow communication for extracting clean air therefrom, wherein the cavity funnels radially outward to a circumferentially extending narrow tip and the bleed apertures are oriented at a tangentially extending angle relative to said main longitudinal axis to allow a tangential velocity component of the bleed air entering the cavity via said apertures during operation of the gas turbine engine to centrifuge particles present in the bleed air radially outward towards the circumferentially extending narrow tip of the cavity and to convey the particles circumferentially thereabout to a particle outlet, the air outlet being positioned radially inwardly from the narrow tip of the cavity. 6. The gas turbine engine of claim 5, further comprising an annular baffle plate connected to a compressor shroud portion of the compressor case adjacent the bleed apertures, the baffle plate extending radially outwardly from the compressor shroud portion toward the narrow tip of the cavity, between the bleed apertures and the air outlet. 7. The gas turbine engine of claim 5, wherein the air outlet is positioned in an upper portion of the compressor case. 8. The gas turbine engine of claim 5, wherein the particle outlet positioned in a circumferential bottom portion of the compressor case. 9. The gas turbine engine of claim 7, further comprising a catch plate connected to the compressor case in the narrow radially-outward tip of the cavity, adjacent the particle outlet and angled with respect to the tangential velocity component of the bleed air, to guide the centrifuged particles into the particle outlet. 10. The gas turbine engine of claim 7, wherein the compressor is a centrifugal compressor and the rotor is an impeller. 11. A method of separating particles from air during operation of a gas turbine engine, the method comprising: extracting bleed air from a compressor gas path into a generally toroidal cavity surrounding the gas path via a plurality of circumferentially interspaced apertures oriented such as to maximize a tangential velocity of the bleed air in said cavity;centrifuging particles radially outwardly into a channel formed in the cavity using the tangential velocity of the bleed air flowing within said cavity, and maintaining a circumferential flow of the bleed air in the cavity to circumferentially convey the particles about the channel to a particle exit;extracting the particles from within the channel of the cavity via the particle exit; andextracting clear air from the cavity via a clean air exit, the clean air being substantially free from the particles. 12. The method of claim 11, further comprising preventing the bleed air from passing directly from the inlet apertures to the clean air outlet of the cavity without first being circumferentially redirected. 13. The method of claim 11, wherein the step of extracting the particles includes evacuating a quantity of the bleed air with the particles. 14. The method of claim 11, wherein the step of extracting the clean air includes extracting the clean air from a location within the cavity that is recessed radially inwardly from the channel. 15. The particle separator of claim 1, wherein the circumferential lower portion of the radially outer narrow tip of the cavity is disposed at a circumferential bottom of the casing surrounding the compressor impeller gas path.