Staged pilots in pure airblast injectors for gas turbine engines

1. A fuel injector for a gas turbine engine comprising:

a main nozzle body defining a central axis and having a main fuel circuit; and

a pilot nozzle body mounted inboard of the main nozzle body, the pilot nozzle body including a pilot air circuit on the central axis with fuel circuitry radially outboard of the pilot air circuit for delivering fuel to a prefilming chamber outboard of the pilot air circuit, the fuel circuitry including

a primary pilot fuel circuit configured and adapted to deliver a fuel flow into the prefilming chamber with a first set of flow characteristics, and

a secondary pilot fuel circuit configured and adapted to deliver a fuel flow into the prefilming chamber with a second set of flow characteristics that is different from the first set of flow characteristics for fuel patternation control by varying relative flow in the primary and secondary pilot fuel circuits.

2. A fuel injector as recited in claim 1 , wherein the primary pilot fuel circuit includes a plurality of first fuel passages, and wherein the secondary pilot fuel circuit includes a plurality of second fuel passages, wherein the first and second fuel passages extend from an upstream portion of the pilot nozzle body to the prefilming chamber thereof.

3. A fuel injector as recited in claim 1 , wherein the primary pilot fuel circuit is configured and adapted to have a lower flow number than the secondary pilot fuel circuit.

4. A fuel injector as recited in claim 1 , wherein the primary pilot fuel circuit includes a plurality of first fuel passages, and wherein the secondary pilot fuel circuit includes a plurality of second fuel passages, wherein the first and second fuel passages extend from an upstream portion of the pilot nozzle body to the prefilming chamber thereof, wherein the first and second fuel passages are in fluid communication with the prefilming chamber by way of a plurality of metering slots, and wherein the number of metering slots of the first fuel passages is different from the number of metering slots of the second fuel passages.

5. A fuel injector as recited in claim 1 , wherein the primary pilot fuel circuit includes a plurality of first fuel passages, and wherein the secondary pilot fuel circuit includes a plurality of second fuel passages, wherein the first and second fuel passages extend from an upstream portion of the pilot nozzle body to the prefilming chamber thereof, wherein the first and second fuel passages are in fluid communication with the prefilming chamber by way of a plurality of metering slots, wherein each metering slot of the first fuel passages is angled at a first angle with respect to a central axis of the pilot nozzle body, wherein each metering slot of the second fuel passages is angled at a second angle with respect to a central axis that is different from the first angle.

6. A fuel injector as recited in claim 1 , wherein the primary pilot fuel circuit includes a plurality of first fuel passages, and wherein the secondary pilot fuel circuit includes a plurality of second fuel passages, wherein the first and second fuel passages extend from an upstream portion of the pilot nozzle body to the prefilming chamber thereof, wherein the first and second fuel passages are in fluid communication with the prefilming chamber by way of a plurality of metering slots, wherein each metering slot of the first fuel passages has a first flow area, and wherein each metering slot of the second fuel passages has a second flow area that is different from the first flow area.

7. A fuel injector for a gas turbine engine comprising:

a main nozzle body defining a central axis and having a main fuel circuit; and

a pilot nozzle body mounted inboard of the main nozzle body, the pilot nozzle body including a pilot air circuit on the central axis with fuel circuitry radially outboard of the pilot air circuit for delivering fuel to a fuel outlet in a downstream portion of the pilot nozzle body,

the fuel circuitry including a primary pilot fuel circuit configured and adapted to deliver fuel to the fuel outlet and a secondary pilot fuel circuit configured and adapted to deliver fuel to the same fuel outlet via a common prefilming chamber defined in the downstream portion of the pilot nozzle body upstream of the fuel outlet.

8. The fuel injector as recited in claim 7 , wherein the primary pilot fuel circuit includes a plurality of first fuel passages, and wherein the secondary pilot fuel circuit includes a plurality of second fuel passages, wherein the first and second fuel passages extend from an upstream portion of the pilot nozzle body to the fuel outlet thereof.

9. The fuel injector as recited in claim 8 , wherein the first and second fuel passages feed into the common prefilming chamber.

10. The fuel injector as recited in claim 8 , wherein the pilot nozzle body includes a fuel swirler outboard of the pilot air circuit and a wherein the prefilmer is mounted outboard of the fuel swirler, wherein the first and second fuel passages are defined in an outboard surface of the fuel swirler, and wherein each of the first fuel passages includes a first fuel inlet in fluid communication with a first opening through the prefilmer, and wherein each of the first fuel passages includes a metering slot in fluid communication with the fuel outlet of the pilot nozzle body.

11. The fuel injector as recited in claim 8 , wherein the pilot nozzle body includes a fuel swirler outboard of the pilot air circuit and wherein the prefilmer is mounted outboard of the fuel swirler, wherein the first and second fuel passages are defined in an outboard surface of the fuel swirler, and wherein each of the second fuel passages extends between the outlet of the pilot nozzle body and a common fuel inlet in fluid communication with a second opening through the prefilmer.

12. The fuel injector as recited in claim 8 , wherein one of the second fuel passages extends between each circumferentially adjacent pair of first fuel passages.

13. The fuel injector as recited in claim 7 , wherein the primary pilot fuel circuit is configured and adapted to have a lower flow number than the secondary pilot fuel circuit.

14. A fuel injector as recited in claim 7 , wherein at least one of the main fuel circuit and pilot fuel circuits includes a diverging prefilming air-blast atomizer.

15. A fuel injector for a gas turbine engine comprising:

a nozzle body including an air circuit on a central axis of the nozzle body with fuel circuitry radially outboard of the air circuit for delivering fuel to a prefilming chamber outboard of the air circuit, the fuel circuitry including:

a first fuel circuit configured and adapted to deliver a fuel flow into the prefilming chamber with a first set of flow characteristics, and

a second fuel circuit configured and adapted to deliver a fuel flow into the prefilming chamber with a second set of flow characteristics that is different from the first set of flow characteristics for fuel patternation control by varying relative flow in the first and second fuel circuits; and

wherein the first fuel circuit of the nozzle body includes a plurality of first fuel passages, and wherein the second fuel circuit of the nozzle body includes a plurality of second fuel passages, wherein the first and second fuel passages extend from an upstream portion of the nozzle body to the prefilming chamber thereof, wherein the first and second fuel passages are in fluid communication with the prefilming chamber by way of a plurality of metering slots and

wherein a number of metering slots of the first passages and a number of metering slots of the second fuel passages have relative to one another a different number of metering slots, a different angle with respect to the central axis of the nozzle body, or a different flow area.

16. The fuel injector as recited in claim 15 , wherein the number of metering slots of the first fuel passages is different from the number of metering slots of the second fuel passages.

17. The fuel injector as recited in claim 16 , wherein each of the first fuel passages is in fluid communication with the prefilming chamber through one metering slot, and wherein each of the second fuel passages is in fluid communication with the prefilming chamber through two metering slots.

18. The fuel injector as recited in claim 15 , wherein each metering slot of the first fuel passages is angled at a first angle with respect to the central axis of the nozzle body for imparting swirl onto fuel flowing therethrough, wherein each metering slot of the second fuel passages is angled at a second angle with respect to the central axis that is different from the first angle.

19. The fuel injector as recited in claim 15 , wherein each metering slot of the first fuel passages has a first flow area, and wherein each metering slot of the second fuel passages has a second flow area that is different from the first flow area.

20. The fuel injector as recited in claim 19 , wherein each metering slot of the first fuel passages has a first depth relative to the central axis, and wherein each metering slot of the second fuel passages has a second depth relative to the central axis that is different from the first depth.