Gas turbine engine with a microwave generator

1. A combustor for a gas turbine engine, the combustor comprising:

a combustion chamber;

at least one fuel spray nozzle operable to deliver a fuel-air mixture into the combustion chamber, wherein during operation of the gas turbine engine the fuel-air mixture is combusted in the combustion chamber, thereby producing a combustion flame;

a microwave generator coupled to a waveguide arranged to guide microwaves from the microwave generator into the combustion chamber such that the microwaves are incident on at least a portion of the combustion flame; and,

a detector operable to detect at least a portion of microwaves reflected by the combustion flame and/or atomised fuel droplets;

wherein the waveguide extends to the combustion chamber through the fuel spray nozzle or one of the fuel spray nozzles.

2. The combustor of claim 1 , wherein the waveguide extends at least partially along the fuel spray nozzle or one of the fuel spray nozzles.

3. The combustor of claim 1 , wherein a swirler is disposed within the fuel spray nozzle.

4. The combustor of claim 3 , wherein the swirler has a bore extending therethrough and the bore provides the waveguide or at least a portion of the waveguide.

5. The combustor of claim 1 , wherein the detector comprises at least one antenna located at a position for receiving at least the portion of the microwaves reflected by the combustion flame and/or atomised fuel droplets.

6. The combustor of claim 5 , wherein the antenna is disposed at an end of the waveguide proximal the combustion chamber.

7. The combustor of claim 1 , wherein the detector is operably connected to a processing means located remotely from the combustion chamber.

8. The combustor of claim 7 , wherein the processing means is arranged to compare an image signal with at least one reference image signal.

9. The combustor of claim 7 , wherein the processing means is arranged to generate one or more control signals to vary directly or indirectly the operation of the gas turbine engine, in order to change the combustion flame.

10. A system for monitoring and/or controlling the operation of a gas turbine engine, the system comprising:

a combustor according to claim 1 ; and

a processing means operably connected to the detector;

wherein the processing means is arranged to compare an image signal with at least one reference image signal.

11. The system of claim 10 , wherein the processing means is arranged to generate one or more control signals to vary directly or indirectly the operation of the gas turbine engine, in order to change the combustion flame.

12. A method of monitoring a combustion flame in a combustor of a gas turbine engine, the method comprising the steps of:

guiding microwaves with a waveguide extending to a combustion chamber through a fuel spray nozzle;

illuminating at least a portion of the combustion flame with the microwaves;

detecting at least a portion of microwaves reflected by the combustion flame and/or atomised fuel droplets; and

analysing the detected microwaves reflected by the combustion flame and/or atomised fuel droplets.

13. The method of claim 12 , wherein analysing the detected microwaves reflected by the combustion flame and/or atomised fuel droplets includes comparing a signal provided by, or derived from, the detected reflected microwaves with a reference signal.

14. The method of claim 12 , wherein, depending upon the results of the analysis of the detected microwaves reflected by the combustion flame and/or atomised fuel droplets, the method further comprises a step of varying operation of the gas turbine engine in order to change the combustion flame.