Combustion staging system

Patent metadata

Field	Value
Publication number	US-10408131-B2
Application number	US-201715428005-A
Country	US
Kind code	B2
Filing date	Feb 8, 2017
Priority date	Feb 23, 2016
Publication date	Sep 10, 2019
Grant date	Sep 10, 2019

Abstract

A combustion staging system includes a splitting unit receiving a metered fuel flow and controllably splitting the received flow into pilot and mains flows. Pilot and mains fuel manifolds distribute fuel. A cooling flow recirculation line provides a cooling flow to the mains manifold during pilot-only operation, and a return section to collect mains manifold cooling flow. The cooling flow enters a delivery section and exits the return section. A fuel recirculating control valve on the delivery section has an open position so that the cooling flow enters the delivery section during pilot-only operation; a shut off position prevents the cooling flow entering the delivery section through the cooling flow orifice during pilot and mains operation. A supplementary valve bleeds or feeds cooling flow. The mains manifold cooling flow pressure is determined by the cooling flow and pressure raising orifices flow numbers, and a control setting of the supplementary valve.

First claim

What is claimed is:

1. A combustion staging system for fuel injectors of a multi-stage combustor of a gas turbine engine, the system including:
a splitting unit which receives a metered fuel flow and controllably splits the metered fuel flow into a pilot fuel flow and a mains fuel flow for injecting respectively at a pilot fuel stage and a mains fuel stage of the injectors to perform staging control of the combustor; and
a pilot fuel manifold and a mains fuel manifold respectively distributing fuel from the splitting unit to the pilot fuel stage and the mains fuel stage;
wherein the splitting unit (1) is operable to select the pilot fuel manifold and deselect the mains fuel manifold for a pilot-only operation in which the pilot fuel flow from the splitting unit is nonzero and the mains fuel flow from the splitting unit is zero, and (2) is operable to select both the pilot fuel manifold and the mains fuel manifold for pilot-and-mains operation in which the pilot fuel flow and the mains fuel flow from the splitting unit are both nonzero;
wherein the system further includes a cooling flow recirculation line having (1) a delivery section arranged to provide a cooling fuel flow to the mains fuel manifold when it is deselected during the pilot-only operation so that the mains fuel manifold remains primed with relatively cool fuel, and (2) a return section arranged to collect the cooling fuel flow from the mains fuel manifold;
wherein the cooling fuel flow enters the delivery section from a high pressure fuel zone of the engine at a cooling flow orifice and exits the return section to a low pressure fuel zone of the engine at a pressure raising orifice;
wherein the system further includes a fuel recirculating control valve on the delivery section adjacent the cooling flow orifice, the fuel recirculating control valve having an open position so that the cooling fuel flow enters the delivery section at the cooling flow orifice during the pilot-only operation, and a shut off position which prevents the cooling fuel flow from entering the delivery section through the cooling flow orifice during the pilot-and-mains operation;
wherein the system further includes a supplementary valve which is controllable to bleed the cooling fuel flow from the recirculation line or feed the cooling fuel flow into the recirculation line; and
wherein the pressure of the cooling fuel flow in the mains fuel manifold is determined by respective flow numbers of the cooling flow orifice and the pressure raising orifice and a control setting of the supplementary valve.

2. The combustion staging system according to claim 1 , further including a controller which controls the control setting of the supplementary valve to meet a target fuel pressure in the mains fuel manifold.

3. A-The combustion staging system according to claim 2 , wherein the controller selects the target fuel pressure which ensures that a fuel pressure of the mains fuel manifold remains above a gas pressure in the combustor.

4. The combustion staging system according to claim 2 , further including a pressure sensor which measures a fuel pressure of the mains fuel manifold, the controller performing feedback control based on the fuel pressure of the mains fuel manifold to meet the target fuel pressure.

5. A-The combustion staging system according to claim 1 , wherein the supplementary valve is a servo-valve which is configured to bleed or to feed continuously variable amounts of the cooling fuel flow.

6. A-The combustion staging system according to claim 1 , wherein the supplementary valve bleeds or feeds the cooling fuel flow from or into the recirculation line adjacent the pressure raising orifice.

7. The combustion staging system according to claim 1 , wherein the supplementary valve is integrated with the splitting unit.

8. The combustion staging system according to claim 1 , further including a recirculating flow return valve on the return section adjacent the pressure raising orifice, the recirculating flow return valve having an open position so that the cooling fuel flow exits the return section at the pressure raising orifice during the pilot-only operation, and a shut off position which prevents the cooling fuel flow from exiting the return section through the pressure raising orifice during the pilot-and-mains operation.

9. The combustion staging system according to claim 1 , wherein the splitting unit is configured to divert a portion of the mains fuel flow into the delivery section during the pilot-and-mains operation, the portion re-joining a remainder of the mains fuel flow in the mains fuel stage of the injectors.

10. The combustion staging system according to claim 9 , wherein the splitting unit has a slidable spool, a position of the spool determining a flow split between an outlet of the splitting unit to the pilot fuel manifold, an outlet of the splitting unit to the mains fuel manifold, and an outlet of the splitting unit to the delivery section of the cooling flow recirculation line.

11. The combustion staging system according to claim 1 , wherein the delivery section includes a delivery manifold which distributes the cooling fuel flow to the injectors en route to the mains fuel manifold.

12. The combustion staging system according to claim 1 , wherein the fuel injectors have integrated mains check valves which are arranged to open when a fuel pressure within the mains fuel manifold exceeds a predetermined fuel pressure relative to a gas pressure in the combustor.

13. The combustion staging system according to claim 1 , wherein the pilot fuel manifold includes a segment restrictable by a lean blow out protection valve to decrease a proportion of the pilot fuel flow delivered to the injectors fed by the segment relative to a total pilot fuel flow delivered to all the injectors of the combustor.

14. A gas turbine engine having the combustion staging system according to claim 1 .

Assignees

• Rolls Royce Plc

Inventors

• Thompson Graham
• Waters Daniel

Classifications

• F05D2270/31

  Fuel schedule for stage combustors · CPC title

• F05D2270/092

  in particular blow-out and relight · CPC title

• F02C9/26

  Control of fuel supply (F02C9/48 takes precedence; fuel valves F02C7/232) · CPC title

• F05D2270/301

  Pressure · CPC title

• F02C7/232

  Fuel valves {(control of fuel supply by means of fuel metering valves F02C9/263)}; Draining valves or systems (valves in general F16K) · CPC title