Diffuser pipe with axially-directed exit

1. A compressor diffuser for a gas turbine engine having a center axis, the compressor diffuser comprising: diffuser pipes having a tubular body including a generally radial portion, a bend portion and a generally axial portion, the generally axial portion having an exit segment extending parallel to the center axis and terminating at a pipe outlet, the pipe outlet being a downstream extremity of the compressor diffuser, the tubular body defining a pipe center axis extending from the radial portion to the pipe outlet, the pipe center axis through the exit segment being the same radial distance from the center axis along the exit segment, the pipe center axis through all of the bend portion disposed radially further from the center axis than the pipe center axis through all of the exit segment, the generally axial portion of the tubular body having an inner wall and an outer wall spaced radially outwardly from the inner wall, a length of the generally axial portion curving radially inwardly from the bend portion toward the exit segment, the inner wall and the outer wall both curving radially inwardly from the bend portion toward the exit segment over the length of the generally axial portion.

2. The compressor diffuser of claim 1 , wherein the tubular body has a length measured from an inlet of the generally radial portion to the pipe outlet, the exit segment having a length of 20% of the length of the tubular body.

3. The compressor diffuser of claim 1 , wherein the center axis and radial lines extending therefrom define a plurality of planes, one of the plurality of planes intersecting the tubular body along the generally axial portion to define a planar profile of the generally axial portion, the planar profile having a slope being a change in a radial distance of the planar profile from the center axis over a length along the center axis, the slope of the planar profile being negative where the generally axial portion curves radially inwardly from the bend portion toward the exit segment.

4. The compressor diffuser of claim 3 , wherein the slope of planar profile along the exit segment is zero.

5. The compressor diffuser of claim 1 , wherein the exit segment is curved circumferentially relative to a portion of the tubular body immediately upstream of the exit segment.

6. The compressor diffuser of claim 1 in combination with a reverse-flow combustor positioned to receive fluid flow from the pipe outlet.

7. A gas turbine engine, comprising:

a compressor having an impeller rotatable about a center axis, and having a radial impeller outlet;

a diffuser with diffuser pipes to receive fluid from the radial impeller outlet, and having a tubular body including a generally radial portion, a bend portion and a generally axial portion, the generally axial portion having an exit segment extending parallel to the center axis and terminating at a pipe outlet being a downstream extremity of the diffuser, the tubular body defining a pipe center axis extending from the radial portion to the pipe outlet, the pipe center axis through all of the bend portion disposed radially further from the center axis than the pipe center axis through all of the exit segment, the generally axial portion of the tubular body having an inner wall and an outer wall spaced radially outwardly from the inner wall, a length of the generally axial portion curving radially inwardly from the bend portion toward the exit segment, the inner wall and the outer wall both curving radially inwardly from the bend portion toward the exit segment over the length of the generally axial portion; and

a reverse-flow combustor downstream of the diffuser.

8. The gas turbine engine of claim 7 , wherein the exit segment is the same radial distance from the center axis along a length of the exit segment.

9. The gas turbine engine of claim 7 , wherein the tubular body has a length measured from an inlet of the generally radial portion to the pipe outlet, the exit segment having a length of 20% of the length of the tubular body.

10. The gas turbine engine of claim 7 , wherein the center axis and radial lines extending therefrom define a plurality of planes, one of the plurality of planes intersecting the tubular body along the generally axial portion to define a planar profile of the generally axial portion, the planar profile having a slope being a change in a radial distance of the planar profile from the center axis over a length along the center axis, the slope of the planar profile being negative where the generally axial portion curves radially inwardly from the bend portion toward the exit segment.

11. The gas turbine engine of claim 10 , wherein the slope of planar profile along the exit segment is zero.

12. The gas turbine engine of claim 7 , wherein the exit segment is curved circumferentially relative to a portion of the tubular body immediately upstream of the exit segment.

13. A method of forming a diffuser pipe of a compressor with a center axis, the diffuser pipe including a generally radial portion, a bend portion and a generally axial portion having an exit segment that terminates at an outlet of the diffuser pipe, the method comprising:

positioning the bend portion of the diffuser pipe radially outwardly from the center axis and from the outlet of the diffuser pipe, orienting the exit segment of the diffuser pipe to be parallel with the center axis, all of the bend portion being radially further from the center axis than all of the exit segment, and curving a length of the axial portion of the diffuser pipe radially inwardly from the bend portion toward the exit segment, wherein an inner wall and an outer wall of the axial portion both curve radially inwardly from the bend portion toward the exit segment over the length of the generally axial portion.

14. The method of claim 13 , wherein orienting the exit segment includes straightening the exit segment to have a same radial distance from the center axis over a length of the exit segment.