Thermal management for injectors

1. An injector for a gas turbine engine, comprising:

a feed arm comprising a primary fluid passage and a secondary fluid passage, a first aperture, a second aperture, and a fluid outlet;

an inlet assembly fixed at an upstream end of the feed arm, the inlet assembly in fluid communication with the first aperture, a first bore and the fluid outlet forming the primary fluid passage, the inlet assembly in fluid communication with the second aperture, a second bore and the fluid outlet forming the secondary fluid passage; and

a tip assembly fixed at a downstream end of the feed arm to the fluid outlet for issuing a spray of fluid,

wherein the primary fluid passage and the secondary fluid passage are monolithically formed within a monolithic structure of the feed arm, wherein the feed arm is devoid of gaps in a thermal conduction path between the structure, the primary fluid passage and the secondary fluid passage, wherein the feed arm is devoid of joints joining the primary fluid passage to the secondary fluid passage, and wherein each of the primary fluid passage and the secondary fluid passage has a flow area that is bounded by the structure,

wherein the secondary fluid passage includes a nonlinear section configured to provide extended residence time for cooling the fluid in the primary fluid passage, wherein the nonlinear section of the secondary fluid passage is serpentine in shape and is axially adjacent a linear section of the primary fluid passage.

2. The injector of claim 1 , wherein the nonlinear section of the secondary fluid passage circles around the linear section of the primary fluid passage.

3. The injector of claim 1 , wherein the nonlinear section of the secondary fluid passage is helical in shape.

4. The injector of claim 1 , the nonlinear section of the secondary fluid passage and a linear section of the secondary fluid passage thereof together are at least three times greater in length than a linear section of a standard fluid passage.

5. The injector of claim 1 , wherein the nonlinear section of the secondary fluid passage extends along a majority of an axial extent of the feed arm.

6. The injector of claim 1 , wherein the primary fluid passage and the secondary fluid passage are formed by additive manufacturing.

7. The injector of claim 1 , further comprising a heat shield disposed around the structure of the feed arm.

8. The injector of claim 7 , wherein the heat shield is formed by additive manufacturing.

9. The injector of claim 7 , wherein the heat shield is monolithically formed with the primary fluid passage and the secondary fluid passage.

10. The injector of claim 1 , wherein the inlet assembly includes separate respective fluid inlets for each of the primary fluid passage and the secondary fluid passage.

11. The injector of claim 1 , further comprising an air shroud additively manufactured monolithic with the tip assembly.

12. A method of manufacturing an injector for a gas turbine engine, comprising:

additively manufacturing a feed arm, an inlet assembly at an upstream end of the feed arm, and a tip assembly at a downstream end of the feed arm;

the feed arm comprising a primary fluid passage and a secondary fluid passage; a first aperture, a second aperture, and a fluid outlet; the first aperture, a first bore and a fluid outlet forming the primary fluid passage; the second aperture, a second bore and the fluid outlet forming the secondary fluid passage,

wherein the primary fluid passage and the secondary fluid passage are monolithically formed within a monolithic structure of the feed arm, wherein the feed arm is devoid of gaps in a thermal conduction path between the structure, the primary fluid passage and the secondary fluid passage, wherein the feed arm is devoid of joints joining the primary fluid passage to the secondary fluid passage, and wherein each of the primary fluid passage and the secondary fluid passage has a flow area that is bounded by the structure,

the inlet assembly has at least one inlet in fluid communication with the primary fluid passage and the secondary fluid passage; and

the tip assembly has the fluid outlet in fluid communication with the primary fluid passage and the secondary fluid passage for issuing a spray of fluid,

wherein the secondary fluid passage includes a nonlinear section configured to provide extended residence time for cooling the fluid in the primary fluid passage, wherein the nonlinear section of the secondary fluid passage is serpentine in shape and is axially adjacent a linear section of the primary fluid passage.

13. The method of claim 12 , further comprising: additively manufacturing a heat shield disposed around the structure of the feed arm.

14. The method of claim 12 , further comprising:

additively manufacturing an air shroud with the tip assembly.