Gas turbine engines and methods for particle separation

A method, comprising:

• operating a compressor of a gas turbine engine to receive a primary gas flow for compression thereof;
• impinging the primary gas flow with airfoils of rotors and stators of the compressor;
• providing the primary gas flow to an impeller of the compressor downstream of the rotors and the stators,
• directing a portion of the primary gas flow through stator extraction holes in radially outer end walls of at least a first stator of the stators as a secondary gas flow, wherein the secondary gas flow includes particles suspended therein;
• directing the secondary gas flow from the stator extraction holes through case extraction holes in a retainer ring of a compressor case radially surrounding the rotors and the stators, the case extraction holes defining passages through the retainer ring, the retainer ring receiving therein the radially outer end walls of the first stator;
• directing the secondary gas flow from the case extraction holes into an interstage bleed plenum defined between surfaces of the compressor case and the impeller to deposit the particles therein;
• and
• operating a bleed air system to provide bleed air to the interstage bleed plenum and thereby remove the particles from the interstage bleed plenum and expel the particles from the gas turbine engine.

An aircraft, comprising:

• a gas turbine engine, comprising:
• a compressor configured to receive a primary gas flow during operation of the gas turbine engine for compression thereof, wherein the compressor includes rotors and stators each having airfoils configured to impinge the primary gas flow and an impeller downstream of the rotors and the stators configured to receive the primary gas flow therefrom, wherein at least a final stage stator of the stators that is disposed immediately upstream of the impeller includes stator extraction holes in radially outer end walls thereof, wherein the stator extraction holes are circumferentially spaced apart to define at least one row of the stator extraction holes, wherein the at least one row is closer to leading edges of the radially outer end walls of the final stage stator than to trailing edges of the radially outer end walls of the final stage stator;
• a compressor case radially surrounding the rotors and the stators of the compressor, the compressor case comprising a retainer ring configured to receive the radially outer end walls of the final stage stator, the retainer ring including case extraction holes defining passages therethrough that provide fluidic communication between the stator extraction holes and an interstage bleed plenum;
• and
• a bleed air system including the interstage bleed plenum defined between surfaces of the compressor case and the impeller, wherein the interstage bleed plenum is in fluidic communication with the case extraction holes, the bleed air system including bleed holes defining passages through the compressor case to provide fluidic communication to the interstage bleed plenum;
• wherein the stator extraction holes and the case extraction holes are configured to, in combination, direct a portion of the primary gas flow to the interstage bleed plenum as a secondary gas flow and thereby remove that particles from the primary gas flow, wherein the bleed air system is configured to remove the particles from the interstage bleed plenum with bleed air and expel the particles from the gas turbine engine,
• wherein the case extraction holes have a larger cross-sectional area than the stator extraction holes, wherein outlets of the stator extraction holes are axially forward of inlets of the case extraction holes.