Dirt extraction apparatus for a gas turbine engine

1. A centrifugal compressor apparatus, comprising:

an impeller mounted for rotation about a central longitudinal axis, the impeller including an impeller disk carrying an array of impeller blades around its periphery;

a diffuser disposed downstream of the impeller, configured to diffuse and turn airflow discharged from the impeller;

an extraction scoop disposed in fluid communication with the impeller and with a plenum disposed adjacent the impeller, and

a dirt collector disposed in fluid communication with the plenum and configured to trap dirt therein and wherein the dirt collector comprises a porous ceramic or metallic material.

2. The apparatus of claim 1 wherein the diffuser is disposed radially outboard of the impeller and includes a plurality of diffuser passageways.

3. The apparatus of claim 1 wherein a shroud assembly defining a convex-curved outer flowpath surface is positioned to closely surround the impeller blades.

4. The apparatus of claim 3 where in the extraction scoop is formed as a part of the diffuser and positioned radially outboard of the shroud.

5. The apparatus of claim 3 where in the extraction scoop is formed as a part of the shroud assembly.

6. The apparatus of claim 3 wherein an outer portion of the shroud assembly is divided into forward and aft segments defining a V-shape, and the extraction scoop is defined by the V-shape.

7. The apparatus of claim 6 wherein a baffle pierced with impingement holes spans the forward and aft segments.

8. The apparatus of claim 1 wherein the extraction scoop has a diffuser shape.

9. The apparatus of claim 1 wherein an annular array of vanes are disposed in the extraction scoop.

10. The apparatus of claim 1 wherein a bypass duct separate from the diffuser communicates with the dirt collector.

11. The apparatus of claim 1 wherein the plenum is defined in part by an outboard plenum wall having an impingement hole formed therein, the impingement hole positioned to direct air flow to the dirt collector.

12. The apparatus of claim 1 further including at least one media wash port disposed in communication with the dirt collector.

13. The apparatus of claim 12 comprising:

an inlet media wash port disposed downstream of the dirt collector; and

an outlet media wash port disposed upstream of the dirt collector.

14. A centrifugal compressor apparatus, comprising:

an impeller mounted for rotation about a central longitudinal axis, the impeller including an impeller disk carrying an array of impeller blades around its periphery;

a diffuser disposed downstream of the impeller, configured to diffuse and turn airflow discharged from the impeller;

an extraction scoop disposed in fluid communication with the impeller and with a plenum disposed adjacent the impeller, wherein an annular array of vanes are disposed in the extraction scoop, and

a dirt collector disposed in fluid communication with the plenum and configured to trap dirt therein.

15. The apparatus of claim 14 further including at least one media wash port disposed in communication with the dirt collector.

16. A centrifugal compressor apparatus, comprising:

an impeller mounted for rotation about a central longitudinal axis, the impeller including an impeller disk carrying an array of impeller blades around its periphery;

a diffuser disposed downstream of the impeller, configured to diffuse and turn airflow discharged from the impeller;

an extraction scoop disposed in fluid communication with the impeller and with a plenum disposed adjacent the impeller, wherein the plenum is defined in part by an outboard plenum wall having an impingement hole formed therein, the impingement hole positioned to direct air flow to the dirt collector, and

a dirt collector disposed in fluid communication with the plenum and configured to trap dirt therein.

17. The apparatus of claim 16 further including at least one media wash port disposed in communication with the dirt collector.