Compressor bleed port structure

1. A compressor bleed port apparatus, comprising:

a compressor shroud which defines a boundary between a primary flowpath and a plenum;

a bleed port including one or more apertures passing through the compressor shroud, each of the one or more apertures having an inlet communicating with the primary flowpath and an outlet communicating with the plenum, and extending along a respective centerline;

wherein each of the one or more apertures is bounded by sidewalls, and includes a diffuser section in which the sidewalls diverge from each other in a downstream direction; and

wherein a diffusing angle between the sidewalls varies over the length of the diffuser section and the diffusing angle has a maximum value at an upstream end of the diffuser section, and a lower value towards a downstream end of the diffuser section.

2. The apparatus of claim 1 wherein the bleed port further comprises a throat of constant flow area positioned upstream of the diffuser section.

3. The apparatus of claim 1 wherein the centerline of at least one of the one or more apertures is curvilinear.

4. The apparatus of claim 3 wherein the centerline of at least one of the one or more apertures is curved in at least two mutually perpendicular planes.

5. The bleed port apparatus of claim 1 wherein the bleed port is configured as a plurality of individual apertures.

6. The bleed port apparatus of claim 1 wherein the bleed port is configured as a continuous slot which defines the one or more apertures.

7. The bleed port apparatus of claim 6 further comprising a plurality of vanes disposed in the slot, defining a plurality of apertures.

8. The apparatus of claim 1 wherein the bleed port is defined within a port wall structure having a first end which joins the compressor shroud and a second end which is spaced away from a wall of the compressor shroud, such that the compressor shroud and the port wall structure define a generally wedge-shaped space therebetween, and the second end of the port wall structure does not contact the compressor shroud.

9. The apparatus of claim 8 wherein a structural support interconnects the port wall structure and the wall of the compressor shroud.

10. The apparatus of claim 1 further comprising an impeller mounted for rotation about a central longitudinal axis inside the compressor shroud.

11. A compressor bleed port apparatus, comprising:

a compressor shroud which defines a boundary between a primary flowpath and a plenum;

a bleed port including one or more apertures passing through the compressor shroud, each of the one or more apertures having an inlet communicating with the primary flowpath and an outlet communicating with the plenum, and extending along a respective centerline;

wherein each of the one or more apertures is bounded by sidewalls, and includes a diffuser section in which the sidewalls diverge from each other in a downstream direction such that they define a diffusing angle between the sidewalls and the diffusing angle varies over the length of the diffuser section;

wherein the centerline of at least one of the one or more apertures is curvilinear;

wherein the bleed port is defined within a port wall structure having a first end which joins the compressor shroud and a second end which is spaced away from a wall of the compressor shroud, such that the compressor shroud and the port wall structure define a generally wedge-shaped space therebetween, and the second end of the port wall structure does not contact the compressor shroud; and

wherein the diffusing angle has a maximum value at an upstream end of the diffuser section, and a lower value towards a downstream end of the diffuser section.

12. The apparatus of claim 11 wherein the centerline of at least one of the one or more apertures is curved in at least two mutually perpendicular planes.

13. The apparatus of claim 11 wherein the bleed port further comprises a throat of constant flow area positioned upstream of the diffuser section.

14. The bleed port apparatus of claim 11 wherein the bleed port is configured as a plurality of individual apertures.

15. The bleed port apparatus of claim 11 wherein the bleed port is configured as a continuous slot which defines the one or more apertures.

16. The bleed port apparatus of claim 15 further comprising a plurality of vanes disposed in the slot, defining a plurality of apertures.

17. The apparatus of claim 11 wherein a structural support interconnects the port wall structure and the wall of the compressor shroud.

18. The apparatus of claim 11 further comprising an impeller mounted for rotation about a central longitudinal axis inside the compressor shroud.