Combustion staging system

Patent metadata

Field	Value
Publication number	US-10288294-B2
Application number	US-201615064245-A
Country	US
Kind code	B2
Filing date	Mar 8, 2016
Priority date	Mar 20, 2015
Publication date	May 14, 2019
Grant date	May 14, 2019

Abstract

A combustion staging system has a splitting unit receiving and splitting metered fuel flow into out-going pilot and mains flows; pilot and mains fuel manifolds receiving the pilot and mains flows; and parallel mains flow scheduling valves distributing the mains flow. The mains flow scheduling valves pass the pilot fuel flow to injector pilot discharge orifices. Each mains flow scheduling valve has a chamber containing a piston, the chamber to a piston pilot side communicating with the pilot fuel manifold and the chamber to a mains side of the piston communicating with the mains fuel manifold. The piston is biased towards a closed pilot-only position preventing flow out of the chamber mains side to the injector mains discharge orifice. The piston is movable under increased pressure in the mains fuel manifold to an open pilot-and-mains position allowing flow out of the chamber mains side to the injector mains discharge orifice.

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 having:
a splitting unit which receives a metered fuel flow and controllably splits the metered fuel flow into out-going pilot and mains fuel flows to perform pilot-only and pilot-and-mains staging control of the combustor;
pilot and mains fuel manifolds which respectively receive the pilot and mains fuel flows; and
a plurality of parallel mains flow scheduling valves which distribute the mains fuel flow from the mains manifold to mains discharge orifices of respective injectors of the combustor and which also pass the pilot fuel flow from the pilot manifold to pilot discharge orifices of the respective injectors;
wherein each mains flow scheduling valve has a chamber containing a movable piston, the chamber to a pilot side of the piston being in fluid communication with the pilot fuel manifold and the chamber to a mains side of the piston being in fluid communication with the mains fuel manifold, the piston being biased towards a closed pilot-only position which prevents flow out of the mains side of the chamber to the mains discharge orifice of the respective injector, and the piston being movable under an increase in pressure in the mains fuel manifold to an open pilot-and-mains position which allows flow out of the mains side of the chamber to the mains discharge orifice of the respective injector, and
wherein the mains flow scheduling valves are configured such that the pilot fuel flow from the pilot manifold to the pilot discharge orifices of the respective injectors passes through the respective chambers on the pilot sides of the pistons, and wherein the pilot side of the piston and the main side of the piston are on opposing sides of the piston.

2. The combustion staging system according to claim 1 , wherein each mains flow scheduling valve further has a cooling flow bypass line providing fluid communication between the mains and pilot sides of its chamber, and the splitting unit is configured to allow a cooling flow through the mains fuel manifold when the mains flow scheduling valves are in their pilot-only positions, wherein the cooling flow passes through the bypass lines to cool the mains fuel manifold during pilot-only operation.

3. The combustion staging system according to claim 2 , wherein the piston shuts off the bypass line when the piston is in its pilot-and-mains position.

4. The combustion staging system according to claim 1 , wherein the splitting unit sends a cooling flow to the mains fuel manifold during pilot-only operation; and wherein the system further has a mains cooling valve which, during pilot-only operation, opens a bypass connection between the mains and pilot fuel manifolds such that the cooling flow passes from the mains fuel manifold to the pilot fuel manifold.

5. The combustion staging system according to claim 4 , wherein the mains cooling valve closes the bypass connection during pilot-and-mains operation.

6. The combustion staging system according to claim 4 , wherein the mains cooling valve reduces the flow area of the bypass connection during pilot-and-mains operation, allowing a leakage flow to pass from the mains fuel manifold to the pilot fuel manifold.

7. The combustion staging system according to claim 4 , wherein each mains flow scheduling valve provides a leak-tight seal between the pilot and mains sides of the chamber when its piston is in its pilot-only position, and a reduced seal between the pilot and mains sides of the chamber when the piston is in its pilot-and-mains position.

8. The combustion staging system according to claim 4 , wherein the mains manifold is configured such that flow through the mains manifold passes in series across respective entrances to the mains flow scheduling valves, the bypass connection between the mains and pilot fuel manifolds comprising parallel first and second fuel lines, the first fuel line extending from the mains to the pilot fuel manifold from an upstream side of the last entrance, the second fuel line extending from the mains to the pilot fuel manifold from a downstream side of the last entrance, and the first and second lines being in fluid communication in the mains cooling valve such that during pilot-and-mains operation fuel circulates around the first and second fuel lines.

9. The combustion staging system according to claim 4 , wherein the mains manifold is configured such that flow through the mains manifold splits into a first fraction which passes in series across respective entrances to a first portion of the mains flow scheduling valves, and a second fraction which passes in second series across respective entrances to a remaining second portion of the mains flow scheduling valves, the bypass connection between the mains and pilot fuel manifolds comprising a fuel line extending from the mains manifold from a location on the mains manifold which is downstream of the last entrances of the first and second portions of the mains flow scheduling valves.

10. The combustion staging system according to claim 1 , wherein the system further has control means for setting a constant pressure differential between the metered fuel flow received by the splitting unit and the pilot fuel flow out of the splitting unit.

11. The combustion staging system according to claim 10 , wherein the splitting unit has a flow splitting valve having a spool whose position is controllable to control the split of the metered fuel flow between the pilot and mains fuel flows, and wherein the control means comprises:
a pressure sensor to measure the pressure differential between the metered fuel flow received by the splitter valve and the pilot fuel flow out of the splitter valve, and/or a further pressure sensor to measure the pressure differential between the metered fuel flow received by the splitter valve and the mains fuel flow out of the splitter valve; and
a device to measure the position of the spool.

12. The combustion staging system according to claim 10 , wherein the control means comprises a pressure drop throttle valve located between the splitting unit and the pilot manifold to controllably throttle the pilot fuel flow and/or between the splitting unit and the mains manifold to controllably throttle the mains fuel flow.

13. The combustion staging system according to claim 10 , wherein the control means comprises:
a flow sensing valve located between the splitting unit and the pilot manifold to measure the flow rate of the pilot fuel flow through the flow sensing valve, or a flow sensing valve located between the splitting unit and the mains manifold to measure the flow rate of the mains fuel flow through the flow sensing valve.

14. The combustion staging system according to claim 1 , further having a plurality of pilot flow scheduling valves, each receiving the pilot fuel flow passed by a respective one of the mains flow scheduling valve, the pilot flow scheduling valves distributing the received pilot fuel flow to their respective pilot discharge orifices when the pilot fuel flow exceeds a cracking pressure set by the pilot flow scheduling valves.

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

Assignees

• Rolls Royce Plc

Inventors

• Griffiths Michael
• Bickley Daniel

Classifications

• F23N2235/24

  Valve details · CPC title

• F23R3/343

  Pilot flames, i.e. fuel nozzles or injectors using only a very small proportion of the total fuel to insure continuous combustion (ignition in gas-turbine plants F02C7/264; pilot flame igniters F23Q9/00) · CPC title

• F02C9/34

  Joint control of separate flows to main and auxiliary burners · CPC title

• F02C9/263

  by means of fuel metering valves · 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